1 ĐẠI HỌC HUẾ TRƯỜNG ĐẠI HỌC SƯ PHẠM NGUYỄN KHOA HIỀN THIẾT KẾ, TỔNG HỢP VÀ ỨNG DỤNG CÁC SENSOR HUỲNH QUANG TỪ DẪN XUẤT CỦA DIMETHYLAMINOCINNAMALDEHYDE VÀ DANSYL Chuyên ngành: Hóa lý thuyết hóa lý Mã số: 62.44.01.19 TÓM TẮT LUẬN ÁN TIẾN SĨ HÓA HỌC HUẾ, NĂM 2016 Công trình hoàn thành tại: Trường Đại học Sư phạm - Đại học Huế Người hướng dẫn khoa học: PGS.TS Dương Tuấn Quang PGS.TS Nguyễn Tiến Trung Phản biện 1: Phản biện 2: Phản biện 3: Luận án bảo vệ trước Hội đồng chấm luận án Tiến sĩ cấp Đại học Huế họp tại: Vào hồi ngày tháng năm 2015 Có thể tìm thấy luận án tại: Thư viện Quốc gia, thư viện trường Đại học Sư phạm Đại học Huế DANH MỤC CÔNG TRÌNH CÔNG BỐ LIÊN QUAN LUẬN ÁN Duong Tuan Quang, Nguyen Van Hop, Nguyen Dinh Luyen, Ha Phuong Thu, Doan Yen Oanh, Nguyen Khoa Hien, Nguyen Van Hieu, Min Hee Lee and Jong Seung Kim (2013), A new fluorescent chemosensor for Hg2+ in aqueous solution, Luminescence., 28, pp 222-225 Nguyen Khoa Hien, Phan Tu Quy, Nguyen Tien Trung, Vo Vien, Dang Van Khanh, Nguyen Thi Ai Nhung and Duong Tuan Quang (2014), A dansyl­diethylenetriamine­thiourea conjugate as a fluorescent chemodosimete for Hg2+ ions in water media, Chemistry Letters, 43, pp 1034-1036 Nguyen Khoa Hien, Nguyen Chi Bao, Nguyen Thi Ai Nhung, Nguyen Tien Trung, Pham Cam Nam, Tran Duong, Jong Seung Kim, Duong Tuan Quang (2015), A highly sensitive fluorescent chemosensor for simultaneous determination of Ag(I), Hg(II), and Cu(II) ions: Design, synthesis, characterization and application, Dyes and Pigments, 116, pp 89-96 Nguyen Khoa Hien, Nguyen Thi Ai Nhung, Ho Quoc Dai, Nguyen Tien Trung, Duong Tuan Quang (2015), A fluorescent sensor based on dansyl-diethylenetriamine-thiourea conjugate: design, synthesis, characterization, and application, Vietnam Journal of Chemistry, 53(5e) pp 541-547 Nguyen Khoa Hien, Nguyen Chi Bao, Phan Thi Diem Tran, Nguyen Van Binh, Duong Tuan Quang (2015), A fluorescent chemosensor based on dimethylaminocinnamaldehydeaminothiourea for highly sensitive simultaneous determination of silver, mercury, and copper ions, The Analytica Vietnam Conference 2015, Ho Chi Minh City, April 15-16, 01-07, pp 13-17 Chemistry Letters, 2014, 43, pp 1034-1036 A dansyl-diethylenetriamine-thiourea conjugate as a fluorescent chemodosimeter for Hg2+ ions in water media Dyes and Pigments, 2015, 116, pp 89-96 A highly sensitive fluorescent chemosensor for simultaneous determination of Ag(I), Hg(II), and Cu(II) ions: design, synthesis, characterization and application MỞ ĐẦU Sensor huỳnh quang tác giả Czarnik Đại học Ohio công bố vào năm 1992 Hiện nay, tuần sensor huỳnh quang công bố giới Điều phương pháp phân tích huỳnh quang thường nhạy với chất phân tích, không đòi hỏi thiết bị máy móc đắt tiền, dễ thực hiện, chi phí phân tích thấp, phân tích chất tế bào sống Các sensor huỳnh quang nghiên cứu ứng dụng phân tích nhiều đối tượng khác nhau, đặc biệt ion kim loại nặng, độc hại thủy ngân (II), đồng (II) bạc (I) Phát triển sensor huỳnh quang thu hút quan tâm nhà khoa học Do đó, sở khoa học cho trình thiết kế, tổng hợp ứng dụng sensor huỳnh quang quan trọng, giúp giảm thời gian, chi phí tăng khả thành công Hiện nay, hoá học lượng tử tính toán hỗ trợ mạnh mẽ phát triển công nghệ thông tin, trở thành công cụ quan trọng nghiên cứu hoá học Nhiều tính chất vật lý hóa học dự đoán làm sáng tỏ từ tính toán Trong đó, nghiên cứu hoàn chỉnh kết hợp tính toán thực nghiệm cho trình thiết kế, tổng hợp ứng dụng sensor huỳnh quang chưa, công bố Ở Việt Nam, sensor huỳnh quang tác giả Dương Tuấn Quang nghiên cứu từ năm 2007, bao gồm: chemosensor phát ion Fe(III), F-, Cs+ Cu(II) dựa calix[4]arene; chemosensor chứa vòng 1,2,3-triazole phát Al(III) chemosensor phát Hg(II) từ dẫn xuất rhodamine Gần đây, dẫn xuất dansyl sử dụng để thiết kế sensor huỳnh quang, hợp chất chúng thường phát huỳnh quang mạnh linh hoạt cấu dẫn xuất chúng Tuy nhiên, chưa có sensor sử dụng dẫn xuất dansyl để phát Hg(II) dựa phản ứng đặc trưng Hg(II), nhằm tăng độ chọn lọc sensor Một chất huỳnh quang khác 4-N,N- dimethylaminocinnamaldehyde, chưa, nghiên cứu để phát triển sensor phát ion Hg(II), Cu(II) Ag(I) Trước nhu cầu thực trạng nghiên cứu sensor huỳnh quang giới Việt Nam, chọn đề tài “Thiết kế, tổng hợp ứng dụng sensor huỳnh quang từ dẫn xuất dimethylaminocinnamaldehyde dansyl” Những đóng góp luận án: - Một chemodosimeter DT từ dẫn xuất dansyl công bố, phát chọn lọc Hg(II) dựa phản ứng đặc trưng Hg(II) - phản ứng dẫn xuất thiourea với amin tạo vòng guanidine có mặt Hg(II) - hoạt động theo chế PET (sự chuyển electron cảm ứng ánh sáng), kiểu bật-tắt (ON-OFF) huỳnh quang, với giới hạn phát giới hạn định lượng Hg(II) tương ứng 50 166 ppb - Một chemosensor DA từ fluorophore 4-N,Ndimethylaminocinnamaldehyde (DACA) công bố, phát đồng thời Hg(II), Cu(II) Ag(I), hoạt động theo kiểu bậttắt huỳnh quang, với giới hạn phát giới hạn định lượng tương ứng là: 2,8 9,5 ppb; 0,8 2,7 ppb; 1,0 3,4 ppb - Một sở khoa học cho trình nghiên cứu phát triển sensor huỳnh quang trình bày, thông qua kết trình kết hợp linh hoạt tính toán lý thuyết thực nghiệm nghiên cứu thiết kế, tổng hợp ứng dụng chemodosimeter DT chemosensor DA CHƯƠNG 1: TỔNG QUAN TÀI LIỆU 1.1 Tổng quan nghiên cứu sensor huỳnh quang 1.1.1 Tình hình nghiên cứu sensor huỳnh quang 1.1.2 Nguyên tắc hoạt động sensor huỳnh quang 1.1.3 Cấu tạo sensor huỳnh quang 1.1.4 Nguyên tắc thiết kế sensor huỳnh quang 1.2 Nguồn ô nhiễm, độc tính, phương pháp phát Hg(II), Cu(II) Ag(I) 1.3 Sensor huỳnh quang phát Hg(II), Cu(II) Ag(I) 1.3.1 Sensor huỳnh quang dựa phản ứng đặc trưng ion kim loại 1.3.2 Sensor huỳnh quang dựa phản ứng tạo phức với ion kim loại 1.3.3 Sensor huỳnh quang dựa tương tác cation – π 1.3.4 Sensor huỳnh quang phát đồng thời Hg(II), Cu(II) Ag(I) 1.4 Sensor huỳnh quang phát Hg(II), Cu(II) Ag(I) dựa fluorophore nhóm dansyl 4-N,Ndimethylaminocinnamaldehyde 1.4.1 Sensor huỳnh quang phát Hg(II) dựa fluorophore nhóm dansyl 1.4.2 Sensor huỳnh quang phát Hg(II), Cu(II) Ag(I) dựa fluorophore 4-N,N-dimethylaminocinnamaldehyde 1.5 Tổng quan ứng dụng hoá học tính toán nghiên cứu sensor huỳnh quang CHƯƠNG N I DUNG VÀ PHƯƠNG PHÁP NGHIÊN CỨU 2.1 Mục tiêu nghiên cứu 2.2 Nội dung nghiên cứu - Nghiên cứu thiết kế, tổng hợp, đặc trưng ứng dụng chemodosimeter DT dựa dẫn xuất dansyl để phát chọn lọc Hg(II) - Nghiên cứu thiết kế, tổng hợp, đặc trưng ứng dụng chemosensor DA dựa DACA phát Hg(II), Cu(II) Ag(I) 2.3 Phương pháp nghiên cứu 2.3.1 Phương pháp nghiên cứu tính toán lý thuyết - Việc xác định cấu trúc hình học bền, lượng điểm đơn thực phương pháp DFT B3LYP/LanL2DZ, sử dụng phần mềm Gaussian 03 - Các thông số lượng tương tác hiệu chỉnh ZPE gồm biến thiên entanpi biến thiên lượng tự Gibbs phản ứng tính toán dựa khác biệt tổng lượng sản phẩm tổng lượng chất tham gia - Tính toán trạng thái kích thích yếu tố phụ thuộc thời gian thực phương pháp TD-DFT mức lý thuyết - Các phân tích AIM NBO tiến hành mức lý thuyết B3LYP/LanL2DZ 2.3.2 Phương pháp nghiên cứu thực nghiệm - Đặc trưng cấu trúc chất khẳng định phổ 1H NMR, phổ 13C NMR, phổ khối MS, phổ hồng ngoại phân tích nhiễu xạ đơn tinh thể tia X - Đặc tính, ứng dụng sensor thực phương pháp quang phổ huỳnh quang UV-Vis CHƯƠNG KẾT QU VÀ TH O LUẬN 3.1 Thiết kế, tổng hợp, đặc trưng ứng dụng DTchemodosimeter phát chọn lọc Hg(II) dựa liên hợp dansyl-diethylenetriamine-thiourea 3.1.1 Nghiên cứu lý thuyết thiết kế, tổng hợp, đặc trưng ứng dụng chemodosimeter DT 3.1.1.1 Khảo sát phương pháp tính toán Để sử dụng mức lý thuyết B3LYP/LanL2DZ cho hệ nghiên cứu, so sánh kết tính toán thực nghiệm cấu trúc dansyl chloride (DC) tiến hành; kết khác biệt Điều cho thấy, mức lý Hình 3.4 Năng lượng HOMO LUMO thuyết chọn áp DC, DNSF, aminothiourea phenyl isothiocyanate B3LYP/LanL2DZ dụng cho hệ nghiên cứu với kết đáng tin cậy 3.1.1.2 Lựa chọn fluorophore receptor cho DT Do chất đầu dùng tổng hợp DT DC không phát huỳnh quang, nên chất huỳnh quang dansyl sunfonamide (DNSF) chọn làm fluorophore, aminothiourea phenyl isothiocyanate (PITC) chọn làm receptor để nghiên cứu Hình 3.4 cho thấy, aminothiourea làm receptor, huỳnh quang sensor hình thành bị dập tắt trình PET từ receptor đến fluorophore Vì vậy, PITC chọn để thiết kế sensor huỳnh quang kiểu bật-tắt 3.1.1.3 Nghiên cứu lý thuyết phản ứng tổng hợp DT a Phản ứng DC với diethylenetriamine Phản ứng DC diethylenetriamine để hình thành trực tiếp sulfonamides không xảy (∆G298 dương) Sulfonamides hình thành thông qua muối amoni (Hình 3.5) Kết tính toán cho thấy, ΔH298 ΔG298 phản ứng (2) âm Theo đó, B sản phẩm thuận lợi mặt nhiệt động Phản ứng (6), phản ứng B sodium hydroxide hình thành P1 thuận lợi mặt nhiệt động, với ΔH298 ΔG298 -47,5 -684,0 kcal.mol-1 b Phản ứng P1 với PITC Phản ứng P1 với PITC có ba sản phẩm (DT, DT-1 DT-2) hình thành (Hình 3.7) Trong đó, ΔH298 ΔG298 phản ứng (8) âm Theo đó, Hình 3.5 Các sản phẩm có phản ứng DC với diethylenetriamine DT sản phẩm thuận lợi mặt nhiệt động Để đánh giá khả phản ứng hóa học xảy ra, điều kiện nhiệt động học, cần phải đảm bảo điều kiện động học Về nguyên tắc, hóa tính toán xác định số tốc độ phản ứng Tuy nhiên, phản ứng phức tạp, việc tính toán nhiều thời gian Thay vào đó, trình tính toán dừng lại mức dự đoán khả phản ứng hướng sản phẩm dựa thông số nhiệt động, sau tiến hành thực nghiệm cho kết nhanh Sự kết hợp linh hoạt tính toán thực nghiệm giảm tải khối lượng công việc tính toán Hình 3.7 Các sản phẩm có phản ứng thực nghiệm P1 với phenyl isothiocyanate 3.1.1.4 Nghiên cứu lý thuyết đặc tính chemodosimeter DT a Cấu trúc phân tử DT Chiều dài liên kết, số đo góc liên kết, góc nhị diện DT Hình 3.8 Hình học bền DT B3LYP/LanL2DZ tính toán Trong đó, tiểu phần DC diethylenetriamine DT thay đổi so với ban đầu b Phân tích phổ UV-Vis DT Phổ UV-Vis DC đạt cực đại 485,2 1055,6 nm; DNSF đạt cực đại 262,0 390,0 nm; DT đạt cực đại 387,5 nm Theo đó, fluorescence of DG was quenched and DT could be used as an ON-OFF fluorescent sensor for selective detection of Hg (II) 3.1.2 Experimental design, synthesis, characteristics and application of chemodosimeter DT 3.1.2.1 Experimental synthesis of chemodosimeter DT a Synthesis of dansyl-diethylenetriamine Diethyltriamine (8.58 mL, 80 mmol) was dissolved in 20 ml CH3CN and cooled to 0oC The solution was added dropwise dansyl chloride (2.70 g, 10 mmol, dissolved in 100 mL CH3CN) The reaction mixture was stirred for hours at room temperature, then was concentrated in vacuo The mixture was added 100 mL of water and was acidified (ca pH=3) by HCl solution before was added 25 mL of ethyl ether, shook, extracted, and removed the organic phase (3 times) Then the obtained aqueous phase was basified with NaOH solution (2M) until the solution became muddy (about 25 mL), followed by the extraction with CH2Cl2, and dried over anhydrous Na2SO4 The solvent was evaporated in vacuo to provide 2.42 g of a dark yellow solid (yield, 72.0%) The structure of dansyldiethylenetriamine was obtained via 1H NMR and FAB-MS spectra b Synthesis of chemodosimeter DT Dansyl-diethyltriamine (337 mg, 1.0 mmol) and phenyl isothiocyanate (0.25 mL, 1.3 mmol) were combined in 30 mL of distilled acetonitrile The reaction solution was allowed to reflux for hours under N2 atmosphere and stirred overnight at room temperature Then the solution was added by 200 mL of water and extracted with 100 mL of CH2Cl2 The organic phase was washed with water and dried over anhydrous MgSO4 The solvent was evaporated under reduced pressure in vacuum concentrator and the residue was purified via silica gel (eluent: CH2Cl2/ethyl acetate = 6/1) The solvent was evaporated under reduced pressure in vacuum concentrator to give 387 mg of DT with 82% yield The structure of DT was confirmed by 1H NMR, 13C NMR and FAB-MS spectra (a) 1.0 Absorbance 0.8 0.6 0.4 0.2 0.0 250 300 350 400 450 Fluorescence Intensity (a u.) 3.1.2.2 Application of DT a The UV-Vis and fluorescence spectra of DT 140 (b) 120 100 80 60 40 20 400 450 500 550 600 650 700 Fluorescence intensity (nm) Wavelength (nm) Fig.3.25 UV-Vis and fluorescence spectra of DT: (a) UV-Vis spectra, DT (10 µM) in C2H5OH /H2O (1/9, v/v), pH ~ 7; (b) fluorescence spectra, DT (10 µM) in C2H5OH/H2O (1/9, v/v), pH ~ 7, excitation wavelength at 330 nm 1.0 (a) Absorbance 0.8 2+ Hg titration 0.6 0.4 0.2 0.0 250 300 350 400 Wavelength (nm) 450 Fluorescence intensity (a u.) As expected from calculations, DT exhibited a characteristic absorption band peaked at 330 nm and gaves rise to an extensively green emission at 529 nm with a quantum yield of 0.11 b UV-Vis and fluorescence titration spectra of DT with Hg(II) Fig.3.26 showed that Hg (II) reacted and changed the UV-Vis, and fluorescence spectra of DT was also as the expectation from theoretical calculation The fluorescence intensity of DT was gradually quenched by increasing the concentration of Hg(II) ions 140 (b) 120 2+ Hg 100 titration 80 60 40 20 450 500 550 600 650 Wavelength (nm) Fig.3.26 The UV-Vis and fluorescence spectra of DT with Hg(II): (a) UV-Vis spectra, DT (10 µM) in C2H5OH/H2O (1/9, v/v), pH ~7, Hg(ClO4)2 (0, 2, 4, 6, 8, 10, 12 µM); (b) Fluorescence spectra, DT (10 µM) in C2H5OH/H2O (1/9, v/v), pH ~7, Hg(ClO4)2 (0, 1, 2, 3, 4, 5, 6.5, 7, 7.5, 8, 9, 10, 12 µM), excitation wavelength at 330 nm 120 2+ (a) 140 DT 0.8 DT + other metal ions 0.6 DT + Hg 2+ 0.4 DT + other metal ions + Hg 2+ 0.2 0.0 250 275 300 325 350 375 400 425 450 Fluorescence intensity (a.u.) 1.0 Absorbance Fluorescence intensity (a u.) c Reaction between DT and Hg(II) Fig.3.27 showed that DT and Hg(II) 100 react in a 1:1 molar ratio The product 80 (DG) of the reaction between DT and 60 Hg(II) were synthesized and its structure 40 was perfectly conformity with the 20 calculated results DG was not 10 12 14 16 fluorescnece When equiv of EDTA [Hg ], µM were added to the resulting solution of the Fig.3.27 The graph for determination of the molar ratio of the reaction between Hg(II) reaction between DT and Hg(II), no and DT: DT 10 µM in C2H5OH/H2O (1/9, v/v) distinct change in the fluorescence spectra pH ~7, emission wavelength at 529 nm, excitation wavelength at 330 nm was observed Therefore, the reaction between DT and Hg (II) was irreversible DT was a fluorescent chemodosimeter d Effects of the competing metal ions 140 DT + other metal ions (b) 120 DT 100 80 DT + other metal ions + Hg 60 40 DT + Hg 2+ 2+ DG 20 400 450 500 550 600 650 Wavelength (nm) Wavelength (nm) Fig.3.31 UV-Vis and Fluorescence spectra of DT in the presence of the metal ions a) UV-vis spectra, b) Fluorescence spectra: DT (10 µM) in C2H5OH/H2O (1/9, v/v) at pH ~7, excitation wavelength at 330 nm i) DT (10 µM); ii) DT + Hg(II) (15 µM); iii) DT + other metal ions including Zn(II), Cu(II), Cd(II), Pb(II), Ag(I), Fe(II), Cr(III), Co(III), Ni(II), Ca(II), Mg(II), K(I) and Na(I) (15 µM; iv) DT + other metal ions + Hg(II) (15 µM); v) DG(10µM) in C2H5OH/H2O (1/9, v/v) Fig.3.31 indicated that DT could detect selectively Hg(II) in the presence of the competing metal ions, including Zn(II), Cu(II), Cd(II), Pb(II), Ag(I), Fe(II), Cr(III), Co(III), Ni(II), Ca(II), Mg(II), K(I) and Na(I) with a 1.5 times higher concentration of DT e Reaction time between Hg (II) and DT The reaction between Hg(II) and DT occurred almost immediately, about 20 seconds after adding Hg(II) to DT solution, which was much faster than announced sensors f Using DT for quantitation of Hg(II) With different concentrations of Hg(II) ranging from 0.5 to 10μM, there were good linear relationships between the variation of fluorescence intensity of DT and Hg(II) concentration The following equations were developed from calibration curves: ΔI529 = (2.8 ± 0.8) + (11.3 ± 0.2) x [Hg(II)], with R=0.999 The limit of detection and quantitation for Hg(II) were identified to be 0.25 and 0.83 µM, or 50 and 166 ppb, respectively 3.2 Design, synthesis, characteristic and application of DAchemosensor based on 4-N,N-dimethylamino cinnamaldehyde derivative for simultaneous determination of Hg(II), Cu(II) and Ag(I) 3.2.1 Theoretical design, synthesis, and characteristic of DA 3.2.1.1 Selection of fluorophore and receptor for DA Fig.3.36 showed that the HOMO and LUMO energy levels of PITC and aminothiourea were not between the HOMO and LUMO energy levels of the DACA fluorophore Therefore, both PITC and aminothiourea were possible to be selected as a receptor Herein, amino thiourea Fig.3.36 The HOMO and LUMO energy values of the DACA, PITC and aminothiourea was selected for the design of an at the B3LYP/LanL2DZ level of theory ON-OFF fluorescent sensor 3.2.1.2 Theoretical synthesis reaction of DA Four products could be formed from the reaction between DACA and aminothiourea (Fig.3.37) Calculated results indicated that the reactions generating DA-1 and DA-2 products did not occur (ΔG298 is positive) ∆H298 and ∆G298 of reactions generating DA-3 and DA products were negative However, ΔG298 and ΔH298 of reaction generating DA product were the most negative Accordingly, DA was thermodynamically favorable product 3.2.1.3 Theoretical characteristics of DA a Molecular structure of DA The bond lengths, bond angles, and dihedral angles of DA were calculated at B3LYP/LanL2DZ level of theory, and compared with Fig.3.37 The possible products from the reaction between DACA and aminothiourea experimental data obtained by X-ray diffraction analysis of crystals of DA The results indicated that the B3LYP/LanL2DZ level of theory was possible to apply to the research system with reliable results b UV-Vis spectral analysis of DA The UV-Vis spectra of DACA showed two bands at 242.5 and Fig.3.38 The optimized geometry of DA at the B3LYP/LanL2DZ level of theory 350.0 nm, DA showed two bands at 278.4 and 395.2 nm The oscillator strength of bands in UV-Vis spectra of DA was stronger than of DACA This result led to expectation that the fluorescent properties of DA would be better than of DACA fluorophore c Fluorescent properties analysis of DA * The fluorescent ability of chemosensor DA Table 3.9 indicated that the transition with the strongest oscillator strength of DA was transition from S0 ground state to S2 excited state, corresponding to the MO61 (HOMO)→MO62 (LUMO) transition, at the wavelength of 395.2 nm There were not any MOs belong to receptor which their energy levels are between MO61 and MO62 So the PET process from receptor to fluorophore did not occur in DA It led to an expectation that DA would be a fluorescent compound The next transition is from S0 ground state to S5 excited state This transition was mainly contributed by MO58→MO62 transition and had a relatively strong oscillator strength, but MO60 belonged to receptor which its energy level is between MO58 and MO62 and the PET process occurred from receptor to fluorophore So this transition did not result in the fluorescence in DA Table 3.9 Calculated excitation energy (E), wavelength (λ), and oscillator strength (f) for lowlaying singlet state of DACA, aminothiourea and DA at B3LYP/LanL2DZ Main E λ f CIC Compound DA DACA Amino thiourea (eV) (nm) S0→S2 orbital transition 61→62 3.14 395.2 1.3602 0.620 S0→S5 58→62 4.45 278.4 0.2861 0.610 61→64 0.199 61→64 -0.166 S0→S2 47→48 3.53 350.8 0.8621 0.614 S0→S5 44→48 5.11 242.6 0.2685 0.358 S0→S2 45→48 0.425 47→50 0.367 18→20 5.43 228.4 0.1540 0.602 19→21 0.178 19→24 -0.124 Fig.3.43 Frontier orbital energy diagram of free fluorophore, receptor and chemosensor DA (The energy levels are relative, not in proportion) * Fluorescent Characteristics of chemosensor DA The effect of solvent polarity and the fluorescence emission from twisted state were surveyed because of the molecular of DA with donor-π-acceptor structure The results showed that the polarization of the solvent did not affect the fluorescence properties of the DA After photo excitation of DA, the transformation from the LE* excited state (planar) to the TICT* excited state (twisted) in S1 excited state was favorable in terms of energy The TICT* excited state with the lowest energy level of S1 excited state was at θ∼90 (θ: dihedral angle between N, N-dimethylamino group and the phenyl ring) The process of twisting simultaneously increased the potential energy surface of S0 ground state and reaches a maximum at θ∼90 As a result, a smallest energy gap between the ground (S0) and the first excited state (S1) was observed It would lead to a red-shift in emission spectra of DA 3.2.2 Experimental synthesis and characteristics of DA 3.2.2.1 Experimental synthesis of DA DACA (175 mg, 1.0 mmol) and aminothiourea (100 mg; 1.1 mmol) were mixed in absolute ethanol (40 mL) The reaction mixture was heated at reflux for hours under a nitrogen atmosphere and then stirred for more hours at room temperature The precipitate was filtered and washed (3 times) with ethanol (5 mL each), then recrystallized from absolute ethanol (25 mL) to obtain the final product DA (207 mg, yield, 83.0%) The structure of DA was confirmed by 1H NMR, FAB-MS, IR spectra and X-ray diffraction analysis of single crystal 3.2.2.2 Experimental characteristics of DA As expected, the free DA exhibited a characteristic absorption band peaked at 390 nm and gaves rise to an extensively green emission at 510 nm with a quantum yield of 0.25 and the Stoke's shift was 120 nm 3.2.3 Application of DA 3.2.3.1 Experimental application of DA a Reaction between DA and 1000 DA + Pb , Cd , Cr DA metal ions 900 Zn , Fe , Co 800 Ni , Ba , Al Fig.3.52 indicated that DA 700 Ca , Mg could be used for detection of K , Na 600 500 Hg(II), Cu(II) and Ag(I) in 400 the presence of other metal DA + Ag , Hg , Cu 300 ions, including Na(I), K(I), 200 100 Pb(II ), Cd(II), Co(II), Ca(II), Ba(II), Mg(II), Zn(II), Fe(II), 450 480 510 540 570 600 630 Wavelength(nm) Ni(II), Al(III) and Cr(III ) Fig.3.52 Fluorescence spectra of DA in the presence b Application of DA for of other metal ions: DA (3µM) in EtOH/H2O (1/9, detection of Hg(II) v/v), metal ions Ag(I), Hg(II), Cu(II), Pb(II), Cd(II), Cr(III), Zn(II), Fe(II), Co(II), Ni(II), Ba(II), Al(III), The results from the survey Ca(II), Mg(II), K(I) Na(I) (15 µM each) excitation wavelength 390 nm on the fluorescence titration spectra of DA with Hg(II) indicated that DA and Hg(II) reacted in a 2:1 molar ratio When 10 equiv of Na2S2O3 were added to the resulting solution of the reaction between DA and Hg(II), the fluorescence intensity was returned to the initial value of free DA It showed that the reaction between DA and Hg(II) was reversible DA was a fluorescent chemosensor When the concentrations of Hg(II) was varies in the range from 15 to 240 ppb, the equation to describe the linear relationship between the variation of fluorescence intensity of DA and Hg(II) concentration was I = (879.9 ± 3.2) + (-2.6 ± 0.0) x [Hg(II)], with R=0.999 The limit of detection and quantitation for Hg(II) were 2.8 and 9.5 ppb, respectively c Application of DA for detection of Cu(II) The fluorescence titration spectra of DA with Cu(II) also indicated that DA and Cu(II) reacted in a 2:1 molar ratio The fluorescence intensity of the resulting solution of the reaction between DA and Cu(II) was returned to the initial value of free DA 2+ Fluorescence intensity (a.u) 2+ 2+ 2+ 2+ 2+ + 2+ 3+ 2+ 3+ 2+ + + 2+ 2+ when adding 10 equiv of EDTA to the solution This result indicated that the reaction between DA and Cu(II) was reversible DA acted as a fluorescent chemosensor for detection of Cu(II) In the concentration range of 4.8 to 67.2 ppb of Cu(II), there was a linear relationship between the variation of fluorescence intensity of DA and concentration of Cu(II) The following equation was developed from calibration curve: I = (882.9 ± 2.6) + (-10.5± 0.1) x [Cu(II)], with R=0.999 The limit of detection and quantitation for Cu(II) were 0.8 and 2.7 ppb, respectively d Application of DA for detection of Ag(I) Survey on the fluorescence titration spectra of DA with Ag(I) led to the conclusion that DA and Ag(I) reacted in a 1:1 molar ratio DA was a fluorescent chemosensor for detection of Ag(I) with the evidence was that the fluorescence intensity of the resulting solution of the reaction between DA and Ag(I) was returned to the initial value of free DA when 10 equiv of Na2S were added to the solution The equation to describe the linear relationship between the variation of fluorescence intensity of DA and concentration of Ag(I) in the range from 16 to 194 ppb was I = (874.0 ± 2.2) + (-3.4 ± 0.0) x [Ag(I)], with R=0.999 The limit of detection and quantitation for Ag(I) were 1.0 and 3.4 ppb, respectively e Application of DA for simultaneous determination of Hg(II), Cu(II), and Ag(I) The experimental results showed that the fluorescence intensity changes of DA by Hg(II) or Cu(II) can be prevented when adding Na2S2O3 or EDTA in the solution, respectively This suggested that it was possible to use DA for simultaneous quantification of Hg(II), Cu(II), and Ag(I) Fig.3.67 showed the ability to use DA for simultaneous quantification of Hg(II), Cu(II), and Ag(I) First, the Ag(I) ions concentration could be quantified based on the variation of fluorescence intensity between the (1) solution) and the (3) solution) Following that the Hg(II) ions concentration could be quantified based on the variation of fluorescence intensity between 700 (3) (4) the (3) solution and the (5) 600 (9) solution) Finally, the Cu(II) 500 (10) 400 ions concentration could be (5) (6) 300 quantified based on the variation (7) (8) 200 of fluorescence intensity 100 (2) between the (3) solution and the 450 500 550 600 Wavelength (nm) (7) solution) The presence of Fig.3.67 Fluorescence spectra to survey on the metal ions, EDTA, and Na2S2O3 possibility of identifying individual ions (Hg(II), did not affect the quantification Cu(II) and Ag(I)) in the mixture: (1) DA; (2) DA + Ag(I) + Hg(II) + Cu(II); (3) DA + Ag(I) + of each metal ions The Hg(II) + Na2S2O3 + Cu(II) + EDTA; (4) DA + Ag(I); (5) DA + Ag(I) + Hg(II) + Cu(II) + relationships between the EDTA; (6) DA + Ag(I) + Hg(II); (7) DA + Ag(I) fluorescence intensity variation + Hg(II) + Na2S2O3 + Cu(II); (8) DA + Ag(I) + Cu(II); (9) DA + Hg(II); (10) DA + Cu(II) (the of DA solution with the concentration of DA, metal ions, Na2S2O3, and concentration of metal ions were EDTA were: 3µM, 0.6µM, 100µM, and 100µM, respectively) found as follows: ∆I[Hg(II)] = (-6.6 ± 3.2) + (2.6 ± 0.0) x [Hg(II)], R=0.999, with concentration range of Hg(II) from 15 to 240 ppb ∆I[Cu(II)] = (-9.7 ± 2.6) + (10.5 ± 0.0) x [Cu(II)], R=0.999, with concentration range of Cu(II) from to 67 ppb ∆I[Ag(I)] = (3.1 ± 2.2) + (3.6 ± 0.0) x [Ag(I)], R=0.999, with concentration range of Ag(I) from 16 to 194 ppb f Survey on the effect of pH The experimental results showed that the DA could detect the Hg(II), Cu(II) and Ag(I) with the broad pH range from to 3.2.3.2 Theoretical application of DA a Stable geometry and interaction energies of complexes The stable geometric structures of the complexes between DA and Ag(I), Hg(II), and Cu(II) with stoichiometry of 1:1, 2:1, and 2:1 are presented in Fig.3.70 There are two stable configurations of complexes between the DA and Ag(I) that are denoted as S1 and S2 In the S1 and S2, the complexes are formed by AgN and AgS bonds; in the S3 and Fluorescence intensity (a.u.) 900 800 (1) S4, the complexes are formed by HgS and CuN bonds S1 In addition, the S2 is stabilized by AgAg bond These bonds are said to be formed based on the S2 calculated results that the contact distances are significantly smaller than the sum of van der Waals radii S3 of relevant atoms The formation of the complexes is thermodynamically favorable, in which the S2 S4 complex is more stable than the S1 complex Fig.3.70 Stable geometries of complexes between DA b AIM analysis and metal ions at the B3LYP/LanL2DZ level of theory (Contact distances in Å and angles in degrees) The results indicated the presence of the bond critical points (BCPs) in each of the AgN, AgS, HgS, and CuN contacts in the S1, S2, S3 and S4 complexes (and AgAg contact in the S2 complex) All values of 2(ρ(r)) at the above BCPs were positive Thus, all these interactions were considered as ionic The result from AIM analysis also discovered the existence of the ring critical points (RCPs), indicating that there was a ring structure present in both the S1 and S2 complexes c NBO analysis The results indicated that the fluorescence quenching of DA upon complexation could be attributed to a transfer of electron density from DA to metal ions, which broke the π-bond conjugated system of the fluorophore in all complexes d Analysis of excitation energies, HOMO, LUMO and the frontier MOs For the S1 complex, the oscillator strengths of the transition from HOMO to LUMO in the excited state was strong, but the excitation energy was small and the fluorescence emission wavelength shifts to the long wavelength, so the fluorescence was not observed in practice In addition, the transfer of electrons between HOMO (where electrons were mainly in the area of metal ions) and LUMO (where electrons were mainly in the fluorophore), was unable to cause the fluorescence because of space distance The other transitions were not from HOMO to LUMO not leading to the fluorescent because of occurring the PET process from the electron pair of HOMO As the result, the fluorescence was quenched Fig.3.72 Frontier orbital energy diagram of DA and S1 in S1 For the S2 complex, in the excited state, the singlet electronic transition was mainly contributed by the transition from S0 to S3, including from MO139 to MO141, and from MO140 to MO142 The transition from MO139 to MO141 did not lead to the fluorescent because of occurring the PET process Fig.3.73 Frontier orbital energy diagram of DA and S2 from MO140 to MO139 The transition from MO140 to MO142 did not lead to the fluorescent, which could be caused by the distance of space as in S1 These results led to the fluorescence quenching in S2 In addition, in both S1 and S2 complex, the electron density in MOs from MO131 to MO140 was mainly distributed in area of metal ions because of the strong transfer of electron density from DA to metal ions The process of transferring electrons from the ground state to the excited state in fluorophore must be crossed the high energy gap, from MO130 to MO141 Therefore, the S1 and S2 complex could not excite to fluoresce by the level of energy such as when exciting the free chemosensor, leading to the fluorescence quenching For S3 complex, the formation of complex led to that the energy gap Fig.3.74 Frontier orbital energy diagram of DA and S3 between HOMO and LUMO was very small, about 0.65 eV In addition, the HOMO→LUMO transition was main transition in S3, resulting to the fluorescence emission wavelength of S3 was larger than 1451 nm and the fluorescence was not observed in practice Fig.3.75 Frontier orbital energy diagram of DA and S4 In the excited state of S4, the formation of complex has led to the transfer of one electron from DA to Cu (II) It led to that MO131 has only one elctron The fluorescence quenching in S4 may be due to the following reasons: the spin multiplicity of the MO131→MO132 transition is 2, so the excited state was doublet, not singlet; the other transitions did not result the fluorescence because occurring the PET process from MO which its energy level was between energy levels of two MO of transition CONCLUSIONS For the first time, a flexible and complete combination between quantum chemical calculations and experimental studies has been successfully applied for research and development of two new fluorescent sensors including chemodosimeter DT and chemosensor DA For chemodosimeter DT, theoretical investigations predicted and oriented for all the processes; the subsequent experimental studies verified and reaffirmed the calculated results For chemosensor DA, the calculation was only used to predict and orient for the experimental survey on the design, synthesis and characteristics of the sensor; the application of chemosensor was first studied by the experiment, and then used theoretical calculations to explain and clarify the nature of the experimental results This flexible combination significantly reduced the volume of theoretical calculations and experimental investigations, increasing the likelihood of success, saving time and used chemicals The fluorophores, receptors and spacers, as well as the synthetic reactions of chemodosmeter DT and chemosensor DA were oriented by calculations and the subsequent experiments have shown a good agreement with the theoretical results The structures, characteristics and applications of chemodosimeter DT and chemosensor DA were determined at the B3LYP/LanL2DZ level of theory with reliable results, through the examination, comparison and confirmation with the experimental results The single-crystal Xray diffraction data of DA were deposited with the Cambridge Crystallographic Data Centre, United Kingdom DT as a fluorescent chemodosimeter could detect selectively Hg (II) with a limit of detection and quantitation of 50 and 166 ppb respectively; the reactions occuring almost instantaneously; using a small amount of organic solvent; and not being affected by other metal ions including Zn(II), Cu(II), Cd(II), Pb(II), Ag(I), Fe(II), Cr(III), Co(III), Ni(II), Ca(II), Mg(II), K(I) and Na(I) The ability to selectively detect Hg (II) of DT was explained by the fact that the Hg(II) caused the characteristic reaction with DT, a reaction between thiourea derivatives and amines in the presence of Hg(II) to form guanidine derivatives The reaction between DT and Hg(II) was studied by the theoritical calculations and was confirmed by 1H NMR, 13C NMR and MS spectra DA as a chemosensor could simultaneously detect Hg(II), Cu(II) and Ag(I) in real samples thanks to the following interesting features: the low limits of detection and quantification, 2.8 and 9.5 ppb, 0.8 and 2.7 ppb, 1.0 and 3.4 ppb, respectively; wide range of pH from to 9; using a small amount of organic solvent; not affected by competing metal ions including Na(I), K(I), Pb(II), Cd(II), Co(II), Ca(II), Ba(II), Mg(II), Zn(II), Fe(II), Ni(II), Al(III) and Cr(III) The reactions to form complexes between DA with Hg(II), Cu(II) and Ag(I), as well as the geometric structures and the bonding characteristics in complexes were studied and identified The fluorescence properties, as well as the fluorescence signal changes before and after the reaction happens between sensor and analytes were investigated by analyzing the excited state and bonding characteristic with using TD-DFT and NBO analysis, respectively Accordingly, Hg (II) caused the desulfurization reaction followed by the formation of guanylation, activated the PET process, and resulted the fluorescence quenching when interacting with DT Meanwhile, the fluorescence quenching of complexes between DA with Hg(II), Cu(II) and Ag(I) was attributed to the fact that the formation of complexes with the strong transfer of electron density from DA to metal ions has led to structural changes and conjugate levels of the π-electron system [...]... độ quang 0.8 Chuẩn độ Hg 0.6 2+ 0.4 0.2 0.0 250 300 350 400 B-ớc sóng (nm) 450 C-ờng độ huỳnh quang (a u.) Nh d oỏn t tớnh toỏn, DT phỏt hunh quang mu xanh lỏ cõy, vi hiu sut lng t l 0,11; bc súng hunh quang cc i 529 nm, bc súng hp th cc i 330 nm b Ph chun UV-Vis v hunh quang DT vi Hg(II) Hỡnh 3.26 cho thy, nh d oỏn t lý thuyt, Hg(II) phn ng v lm thay i ph UV-Vis v ph hunh quang ca DT Cng hunh quang. .. sensors is still unpublished, or very little published In Vietnam, the fluorescent sensors have been studied by Duong Tuan Quang since 2007, including: calix[4]arene based chemosensors for determination of Fe(III), F-, Cs+ and Cu(II) ions; chemosensor based on 1,2,3-triazole for determination of Al(III) ions; and chemosensor based on rhodamine derivative for determination of Hg(II) ions Recently, dansyl. .. ng gia DA v Cu(II) cng theo t l 2:1 v s mol Cng hunh quang dung dch phn ng gia DA v Cu(II) cng tr li ban u nh DA t do nu thờm EDTA vi nng gp 10 ln so vi Cu(II)) DA l chemosensor phỏt hin Cu(II) C-ờng độ huỳnh quang (a.u) 2+ 2+ 2+ 2+ 2+ 2+ + 2+ 2+ 3+ 3+ 2+ + + 2+ 2+ 18 C-ờng độ huỳnh quang (a.u.) Trong khong nng Cu(II) t 4,8 n 67,2 ppb, cng hunh quang dung dch DA quan h tuyn tớnh cht ch vi nng Cu(II)... cụng trong nghiờn cu phỏt trin hai sensor hunh quang mi l chemodosimeter DT v chemosensor DA i vi chemodosimeter DT, tớnh toỏn ó d oỏn v nh hng cho tt c cỏc quỏ trỡnh; nghiờn cu thc nghim sau ú ó kim chng v khng nh li cỏc kt qu tớnh toỏn i vi chemosensor DA, tớnh toỏn ch dựng d oỏn v nh hng cho thc nghim giai on thit k, tng hp v c trng ca sensor; ng dng ca chemosensor DA c nghiờn cu trc t thc nghim,... 6 c tớnh hunh quang, cng nh s thay i tớn hiu hunh quang trc v sau khi cỏc sensor tng tỏc vi cht phõn tớch ó c nghiờn cu thụng qua phõn tớch trng thỏi kớch thớch bng phng phỏp TD-DFT v nghiờn cu bn cht cỏc liờn kt t phõn tớch NBO Theo ú, Hg(II) gõy nờn phn ng tỏch loi lu hunh v úng vũng guanidine, kớch hot quỏ trỡnh PET, dn n dp tt hunh quang khi tng tỏc vi DT Trong khi, hunh quang dp tt trong cỏc phc... (a) DT Mật độ quang 0.8 DT + Các ion kim loại khác 0.6 2+ DT + Hg 0.4 2+ DT + Các ion kim loại khác + Hg 0.2 0.0 250 275 300 325 350 375 400 425 450 C-ờng độ huỳnh quang (a.u.) 1.0 DT + Các ion kim loại khác (b) 140 DT 120 100 80 DT + Các ion kim loại khác + Hg 60 40 DT + Hg 2+ DG 20 0 400 450 500 550 600 650 B-ớc sóng (nm) B-ớc sóng (nm) Hỡnh 3.31 Ph UV-Vis v ph hunh quang DT trong s hin din cỏc ion... application of chemodosimeter DT and chemosensor DA, a scientific basis for research and development of new fluorescent sensors was presented Chapter 1 OVERVIEW 1.1 Overview of fluorescent sensors 1.1.1 Current situation of fluorescent sensors 1.1.2 Operating principles of fluorescent sensors 1.1.3 Structure of fluorescent sensors 1.1.4 Design principles of fluorescent sensors 1.2 The sources of pollution,... Quoc Dai, Nguyen Tien Trung, Duong Tuan Quang (2015), A fluorescent sensor based on dansyl- diethylenetriaminethiourea conjugate: design, synthesis, characterization, and application, Vietnam Journal of Chemistry, 53(5e) pp 541547 5 Nguyen Khoa Hien, Nguyen Chi Bao, Phan Thi Diem Tran, Nguyen Van Binh, Duong Tuan Quang (2015), A fluorescent chemosensor based on dimethylaminocinnamaldehydeaminothiourea... nm; DA t Hỡnh 3.38 Hỡnh hc bn ca DA ti B3LYP/LanL2DZ cc i bc súng 278,4 v 395,2 nm Ph hp th ca DA cú cng mnh hn DACA Kt qu ny a n k vng c tớnh hunh quang ca DA tt hn DACA c Phõn tớch c tớnh hunh quang ca chemosensor DA * Kh nng phỏt hunh quang trong chemosensor DA Bng 3.9 cho thy, trng thỏi kớch thớch cú cng dao ng mnh nht ca DA l t S0S2, bc súng 395,2 nm, ng vi bc chuyn t MO61 (HOMO)MO62 (LUMO) Do... fluorescent sensors for detection of Hg(II), Cu(II) and Ag(I) ions From demand and situation of studying the fluorescent sensors in the world and Vietnam, we conducted the project "Design, synthesis, and application of fluorescent sensors based on dimethylaminocinnamaldehyde and dansyl derivatives" New findings of the thesis: - A new fluorescent chemodosimeter DT has been reported with using derivatives of dansyl ... chemosensor DA CHNG 1: TNG QUAN TI LIU 1.1 Tng quan nghiờn cu v sensor hunh quang 1.1.1 Tỡnh hỡnh nghiờn cu sensor hunh quang 1.1.2 Nguyờn tc hot ng ca sensor hunh quang 1.1.3 Cu to ca sensor. .. 1.3.2 Sensor hunh quang da trờn cỏc phn ng to phc vi ion kim loi 1.3.3 Sensor hunh quang da trờn tng tỏc cation 1.3.4 Sensor hunh quang phỏt hin ng thi Hg(II), Cu(II) v Ag(I) 1.4 Sensor hunh quang. .. quang 1.1.4 Nguyờn tc thit k cỏc sensor hunh quang 1.2 Ngun ụ nhim, c tớnh, phng phỏp phỏt hin Hg(II), Cu(II) v Ag(I) 1.3 Sensor hunh quang phỏt hin Hg(II), Cu(II) v Ag(I) 1.3.1 Sensor hunh quang