Porphyrins Fused with Strongly Electron-Donating 1,3-Dithiol-2-ylidene Moieties: Redox Control by Metal Cation Complexation and Anion Binding

Abstract

A new class of redox-active free base and metalloporphyrins fused with the 1,3-dithiol-2-ylidene subunits present in tetrathiafulvalene, termed MTTFP (M = H2, Cu, Ni, Zn), have been prepared and characterized. The strong electron-donating properties of MTTFP were probed by electrochemical measurement and demonstrated that oxidation potentials can be tuned by metalation of the free base form, H2TTFP. X-ray crystal structures of H2TTFP, ZnTTFP, and CuTTFP revealed that a severe saddle-shape distortion was observed with the dithiole rings bent out of the plane toward one another in the neutral form. In contrast, the structure of the two-electron oxidized species (CuTFFP(2+)) is planar, corresponding to a change from a nonaromatic to aromatic structure upon oxidation. A relatively large two-photon absorption (TPA) cross-section value of H2TTFP(2+) (1200 GM) was obtained for the free base compound, a value that is much higher than those typically seen for porphyrins (<100 GM). Augmented TPA values for the metal complexes were also seen. The strong electron-donating ability of ZnTTFP was further enhanced by binding of Cl(-) and Br(-) as revealed by thermal electron-transfer between ZnTTFP and Li(+)-encapsulated C60 (Li(+)@C60) in benzonitrile, which was "switched on" by the addition of either Cl(-) or Br(-) (as the tetrabutylammonium salts). The X-ray crystal structure of Cl(-)-bound ZnTTFP was determined and provided support for the strong binding between the Cl(-) anion and the Zn(2+) cation present in ZnTTFP.

Porphyrin Derivative Nanoformulations for Therapy and Antiparasitic Agents

“…A wide variety of porphyrins and analogues have been developed and explored as powerful functional tools and as building blocks of supramolecular systems given their tunability, rich coordination chemistry, strong light absorption, and high light emission properties [70][71][72][73][74][75][76][77]. Such features conferred to these molecules a range of biological, photochemical, and photophysical properties with relevant and direct application on diseases' treatment [19,78,79], biological imaging [19,80], and analytical methods [81,82], as well as applications in industrial [83], photocatalytic [84], molecular photovoltaics [85,86], and nonlinear optics (NLO) devices [87].…”

A Fully Charge‐Delocalized Two‐Dimensional Porphyrin System with Two Different Class III States

“…Asimilar deformation was reported for porphyrin-TTF (TTF = tetrathiafulvalene) conjugates with the quinoidal forms,w hich are also nonaromatic. [29] iii)DFT calculationso fc ompounds 1' and 1' 2 + + :I no rder to clarify the electronic structure of the dicationics pecies, DFT calculations werep erformed for complexes 1' and 1' 2 + . [30] Both compounds 1' and 1' 2 + are of virtually fourfold symmetry and selected bond lengths andapart of the Kohn-Shamo rbitals are shown in Table 1a nd Figure1 1, respectively.T he calculated bond lengths for the RuÀCCÀCm oieties of compounds 1' and 1' 2 + agree wellw ith the bond lengths observed for compound 1 and [1 2 + ](PF 6 ) 2 .F or complex 1',t he HOMO is distributed over the four RuÀCCm oieties and the porphyrin a 2utype orbital, whereas the LUMOs are virtually degenerated and are composed of the porphyrin e gx -type orbitals coupled with some RuÀCCc ontribution.…”

Efficient Charge Separation in Li+@C60 Supramolecular Complexes with Electron Donors

“…[52] The TEA + cation is known to bind effectively to the TTF-C4P cavity, thereby repelling Li [52] Similarly, it has been reported that porphyrins fused with the 1,3-dithiol-2-ylidene subunits present in tetrathiafulvalene (MTTFP) and Li + @C 60 underwent thermal electron transfer through complex formation mediated by anion binding. [56] 60 )* as a strong electron acceptor in photoinduced electron-transfer reactions with various electron donors. [59] The rate constants of electron transfer (k et ) from various electron donors to 3 (Li + @C 60 )* are significantly larger than those to C 60 when the rate constants are less than the diffusion-limited value.…”