Preparation And Properties Of Charge-Transfer Compounds Based On TTF Derivatives

Tetrathiafulvalene(TTF) and its derivitives are star molecules and have been used in many areas, such as conductor, photoelectric materials and supramolecular chemistry system due to their electron-donor ability, redox properties, and their stable cations. The chargr-transfer compounds which are constructed by TTF have been intensively studied, but the study often foucus on D-π-A system in which electron donor and acceptor are linked by π connector. There are few on {[cation]n+·[TTFs]n–} ion pair charge-transfer(IPCT) salts and electron-proton coupled transport system. By introducing organic functional molecules into TTF system, new charge-transfer(CT) compounds with photocurrent response properties were obtained. The major contents we researched are as follws:In introduction, the properties and applications of TTF derivatives such as organic photoelectric material, chemical sensor, and molecular device are reviewed briefly. Recent researches on TTF-carboxylates have been summarized. CT compounds concerned with TTF or viologen are also reviewed.In chapter 2, in order to investigate redox and proton transfer coupled process, we designed a proton transfer system of redox-active acid-base assemblies, dimethylthio-tetrathiafulvalene dicarboxylic acid(H2L) coupled with pyridine(py), 2,2’-bipyridine(2,2’-bpy), and 4,4’-bipyridine(4,4’-bpy), respectively. We got three new compounds, Hpy?HL(1), H(2,2’-bpy)?HL(2), and H2(4,4’-bpy)?2(HL)(3). The nature of the hydrogen bonds in crystals was characterized by X-ray single crystal analysis. The 1H NMR chemical shifts of the pyridines and the redox potential shifts of the tetrathiafulvalene moiety indicate that there exist the proton-transfer and strong hydrogen-bonding interaction between the acid and the bases in aprotic solvents. The results of cyclic voltammetry show a two-step square reaction with a redox and proton IV transfer coupled mechanism.In chapter 3, in order to study the effect of different conjugated systems on molecular packing and charge-transfer interactions, three viologen derivatives with different conjugated structures were introducing into TTF-bicarboxylic acid system. A series of {[cation]n+·[TTFs]n–} ion pair charge-transfer(IPCT) salts in basic formula MV(HL)2(4), Me Bpe(HL)2(5) and Me Bpa(HL)2(6) was synthesized and their structures were characterized by X-ray single crystal analysis. The charge-transfer from anion to cation measured by UV-vis, CV, ESR and theoretical calculation. π-extended Me Bpe compound 5 shows the most effective cation–anion interaction. MV compound 4 takes the second place. No effective interaction is found for the non-conjugated Me Bpa compound 6. Photocurrent responses of these compounds are consequently studied and the results agree with the intensity of charge-transfer.In chapter 4,in order to explore the relations of alkyl chain length to molecular structure and film morphologies, H2 L and four different alkyl viologen dications(Cn V2+) are used to organize charge-transfer salts, generally formulated as [(Cn V)(HL)2] [n = 4(7), 8(8), 12(9) and 16(10)]. 7–9 are characterized by single crystal X-ray structural analysis. The charge-transfer from anion to cation was measured by UV-vis, CV and 1H NMR. Lengthening the alkyl chain of bipyridinium cation weakenes the charge-transfer interaction between two components in crystal. Photocurrent intensity was measured, 7 > 8 > 9 = 10. Their film-form property and the photocurrent response properties of the film were also studied. Their film morphologies change from crystals to fused crystals, band-like structures and finally smooth film with the increase of alkyl chain length. Photocurrent intensity of the film modified electrodes(in the order 8 > 7 = 9 > 10) is different from the crystal sample modified electrodes, because both the interion interaction and the film–forming property should be considered for the film electrodes.In chapter 5, we newly designed and synthesized three ligand-to-ligand charge-transfer(LLCT) metal-organic frameworks(MOFs). These compounds are formulated as [Mn L(4,4’-bpy)(H2O)]n·n CH3CN(11), [Mn L(bpe)0.5(DMF)]n·2n H2O(12) and [Mn L(bpa)(H2O)]n·2n H2O(13). The X-ray single crystal diffractions show that complexes 11–13 are all two-dimensional(2-D) coordination polymers with different frameworks in crystal lattices. Charge-transfer(CT) interactions within these MOFs are visually apparent in colors and vary according to the conjugated states of the bipyridine ligands(bpy, bpe, and bpa). Results show that the charge-transfer occurs from ligand L to bipyridine. The intensity of the LLCT is in the order of 12 >> 11 > 13 investigated by UV-vis and ESR, which indicates that the intensity of CT is not only related to the bipyridyl conjugated state but also to the π…π interaction between the ligands. Photocurrent responses of these compounds are consequently studied and the results are in agreement with the intensity of charge–transfer and linearly related to the LLCT energy.