Four coordination polymers, namely, [Zn(HL1)(L2)]·HO (1), [Cd(HL1)(L2)]·HO (2), [Zn(L1)(L3)]·HO (3), and [Cd(L1)(L3)] (4) (HL1 = (3,5-dicarboxyl-phenyl)-(4-(2'-carboxyl-phenyl)-benzyl)ether, HL2Cl = 1,1'-bis(4-carboxy-benzyl)-4,4'-bipyridinium dichloride, and L3Cl = 1,1'-dimethyl-4,4'-bipyridylium dichloride), have been synthesized hydrothermally. The structures of compounds 1-4 have been determined by single-crystal X-ray diffraction analyses, and further characterized by elemental analyses, infrared (IR) spectra, powder X-ray diffraction (PXRD) analyses, and thermogravimetric analyses. Compounds 1 and 2 display three-dimensional 2-fold interpenetrating frameworks, whereas compounds 3 and 4 exhibit two-dimensional layer structures. These compounds display photochromic behaviors from pale yellow to green under UV light, visible light, or sunlight. The photochromic mechanisms of these compounds have been studied by IR spectra, PXRD analyses, UV-vis absorption spectra, electron paramagnetic resonance spectra, density functional theory calculations, and X-ray photoelectron spectroscopy. The capabilities of compounds 1 and 2 as inkless and erasable printing media have also been tested. Moreover, the photomodulated fluorescence of these compounds has also been investigated.

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Some viologen-containing compounds displaying thermo/photochromic behaviors which can be used as inkless print media and anti-counterfeiting materials have been reported.

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We use time-dependent density functional theory methods to discuss the absorption spectra, electronic transition properties, and photovoltaic performance of metalloporphyrin−polyoxometalates (POM) complexes for p-type dye-sensitized solar cells (DSSCs). The results show that the energy levels of the frontier molecular orbitals for dyes 2−6 match the requirements of p-type DSSCs. The absorption spectra of dyes 2−6 exhibit larger and broader absorptions compared to that of dye 1 by the introduction of POM. In addition, the photovoltaic performances of dyes 2−6 are suitable for high-efficiency DSSCs. This paper is expected to advance the design of metalloporphyrin−POM hybrid dyes with excellent performance in DSSCs.

Vibrational excitations provoked by coupling effects during charge transport through single molecules are intrinsic energy dissipation phenomena, in close analogy to electron–phonon coupling in solids. One fundamental challenge in molecular electronics is the quantitative determination of charge-vibrational (electron–phonon) coupling for single-molecule junctions. The ability to record electron–phonon coupling phenomena at the single-molecule level is a key prerequisite to fully rationalize and optimize charge-transport efficiencies for specific molecular configurations and currents. Here we exemplarily determine the pertaining coupling characteristics for a current-carrying chemically well-defined molecule by synchronous vibrational and current–voltage spectroscopy. These metal-molecule-metal junction insights are complemented by time-resolved infrared spectroscopy to assess the intramolecular vibrational relaxation dynamics. By measuring and analyzing the steady-state vibrational distribution during transient charge transport in a bis-phenylethynyl-anthracene derivative using anti-Stokes Raman scattering, we find ∼0.5 vibrational excitations per elementary charge passing through the metal-molecule-metal junction, by means of a rate model ansatz and quantum-chemical calculations.

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