A Donor-Acceptor Tetrathiafulvalene Ligand Complexed to Iron(II): Synthesis, Electrochemistry, and Spectroscopy of Fe(phen)(2)(TTF-dppz)(PF6)(2)

The synthesis and photophysical properties of the complex Fe(phen)(2)(TTF-dppz)(2+) (TTF-dppz = 4',5'-bis-(propylthio)tetrathiafulvenylidipyrido3,2-a:2',3'-c-phenazine, phen = 1,10-phenanthroline) are described. In this complex, excitation into the metal ligand charge transfer bands results in the population of a high-spin state of iron(II), with a decay lifetime of approximately 1.5 ns, in dichloromethane, at room temperature. An intraligand charge transfer state can also be obtained and has a lifetime of 38 ps. A mechanism for the different states reached is proposed based on transient absorption spectroscopy.

A Pt(II) complex with both a phenanthroline and a tetrathiafulvalene-extended dithiolate ligand: Synthesis, crystal structure, electrochemical and spectroscopic properties

The reaction of 4,5-bis(2'-cyanoethylsulfanyl)-4',5'-dipropylthiotetrathiafulvalene with Pt(phen)Cl-2 (phen = 1,10-phenanthroline) with CsOH as base in CH3OH-THE affords the target complex I in 44% yield. This complex crystallizes in the monoclinic space group P2(1)/c, M = 790.01, a = 12.1732(12), b = 15.851(2), c = 14.5371(16) angstrom, beta = 107.693(12)degrees, V = 2672.4(5) angstrom(3) and Z = 4. It undergoes two reversible single-electron oxidation and two irreversible reduction processes. An intense electronic absorption band at 15200 cm(-1) (658 nm) in CH2Cl2 is assigned to the intramolecular mixed metal/ligand-to-ligand charge transfer (LLCT) from a tetrathiafulvalene-extended dithiolate-based HOMO to a phenanthroline-based LUMO. This band shifts hypsochromically with increasing solvent polarity. Systematic changes in the optical spectra upon oxidation allow precise tuning of the oxidation states of 1 and reversible control over its optical properties. Irradiation of 1 at 15625 cm(-1) (640 nm) in glassy solution below 150K results in emission from the (LLCT)-L-3 excited state. GRAPHICS (C) 2013 Elsevier Ltd. All rights reserved.

Tetrathiafulvalene - Benzothiadiazoles as Redox-Tunable Donor - Acceptor Systems: Synthesis and Photophysical Study

Electrochemical and photophysical analysis of new donoracceptor systems 2 and 3, in which a benzothiadiazole (BTD) unit is covalently linked to a tetrathiafulvalene (TTF) core, have verified that the lowest excited state can be ascribed to an intramolecular-charge-transfer (ICT) (TTF)*(benzothiadiazole) transition. Owing to better overlap of the HOMO and LUMO in the fused scaffold of compound 3, the intensity of the 1ICT band is substantially higher compared to that in compound 2. The corresponding CT fluorescence is also observed in both cases. The radical cation TTF+. is easily observed through chemical and electrochemical oxidation by performing steady-state absorption experiments. Interestingly, compound 2 is photo-oxidized under aerobic conditions.

Large π-Conjugated Chromophores Derived from Tetrathiafulvalene

A large π-conjugated chromophore composed of two dipyrido[3,2-a:2′,3′-c]phenazine units directly fused to the central tetrathiafulvalene core has been prepared as a bridging ligand and its strong binding ability to Ru2+ to form a new dinuclear complex is presented. The electronic absorption and luminescence spectra and the electrochemical behavior of the free ligand and the Ru2+ complex have been investigated in detail. The free ligand shows a very strong band in the UV region consistent with ligand-centered π–π* transitions and an intense broad band in the visible region that corresponds to an intramolecular charge-transfer (ILCT) transition. Upon coordination, a metal-to-ligand charge-transfer band appears at 22520 cm−1, and the ILCT band is bathochromically shifted by 1620 cm−1. These electrochemically amphoteric chromophores have also been characterized by spectro-electrochemical methods. The oxidized radical species of the free ligand show a strong tendency to undergo aggregation, in which long-distance attractive interactions overcome the electrostatic repulsion. Moreover, these two new chromophores reveal an ILCT fluorescence with large solvent-dependent Stokes shifts and quantum efficiencies of 0.052 for the free ligand and 0.016 for its dinuclear Ru2+ complex in CH2Cl2.

A Compact Tetrathiafulvalene-Benzothiadiazole Dyad and Its Highly Symmetrical Charge-Transfer Salt: Ordered Donor π-Stacks Closely Bound to Their Acceptors

A compact and planar donor–acceptor molecule 1 comprising tetrathiafulvalene (TTF) and benzothiadiazole (BTD) units has been synthesised and experimentally characterised by structural, optical, and electrochemical methods. Solution-processed and thermally evaporated thin films of 1 have also been explored as active materials in organic field-effect transistors (OFETs). For these devices, hole field-effect mobilities of μFE=(1.3±0.5)×10−3 and (2.7±0.4)×10−3 cm2 V s−1 were determined for the solution-processed and thermally evaporated thin films, respectively. An intense intramolecular charge-transfer (ICT) transition at around 495 nm dominates the optical absorption spectrum of the neutral dyad, which also shows a weak emission from its ICT state. The iodine-induced oxidation of 1 leads to a partially oxidised crystalline charge-transfer (CT) salt {(1)2I3}, and eventually also to a fully oxidised compound {1I3}⋅1/2I2. Single crystals of the former CT compound, exhibiting a highly symmetrical crystal structure, reveal a fairly good room temperature electrical conductivity of the order of 2 S cm−1. The one-dimensional spin system bears compactly bonded BTD acceptors (spatial localisation of the LUMO) along its ridge.

A quinoxaline-fused tetrathiafulvalene-based sensitizer for efficient dye-sensitized solar cells

A new quinoxaline-fused tetrathiafulvalene-based sensitizer has been prepared and characterized. The resulting power conversion efficiency of 6.47% represents the best performance to date for tetrathiafulvalene-sensitized solar cells.