In this work, efficient trans ⇌ cis photoswitchings of 4-(4-cyano)styrylpyridine (stpyCN) coordinated to organometallic bipyridyl tricarbonyl rhenium(I) complexes, fac-[Re(CO)(NN)( trans-stpyCN)], where NN = 2,2'-bipyridine (bpy) or 4,4'-dimethyl-2,2'-bipyridine (dmb), are described. For both complexes, the true trans-to- cis quantum yields determined by H NMR spectroscopy are similar at 313, 334, and 365 nm irradiations (Φ ∼ 0.45), with a small decrease at 404 nm (Φ ∼ 0.37). The investigated complexes also exhibit significant quantum yields for the reversible cis-to- trans photoreactions (Φ = 0.22). The luminescent properties of these complexes were also analyzed in different media to elucidate a key role of the IL state in photophysical and photochemical processes, giving new insights on their intriguing photobehavior.

A strategic methodology has been developed to effectively synthesize the fac-[Re(CO) 3 (dcbH 2 )(trans-stpy)] + complex, where dcbH 2 = 2,2′-bipyridine-4,4′-dicarboxylic acid and trans-stpy = trans-4-styrylpyridine, which has been designed to efficiently absorb visible light. The complex exhibits outstanding trans-to-cis photoisomerization with 436 nm irradiation (Φ trans→cis = 0.50 ± 0.03), in contrast to the photochemical behavior previously reported in the literature (

This review summarizes investigations carried out at the Laboratory of Photochemistry and Energy Conversion (LFCE) in the University of São Paulo dealing with design and characterization of ruthenium(II), rhenium(I) and iridium(III) polypyridine complexes with desired photochemical and photophysical properties in light of the development of optoelectronics and photoinduced energy conversion systems. First, the breakthroughs on molecular engineering of emissive Re I , Ru II and Ir III complexes for the development of highly efficient light-emitting devices, such as organic light-emitting diodes (OLEDs) and light-emitting electrochemical cells (LECs), are presented. Then, the photochemical and photophysical properties of fac-[Re(CO) 3 (NN)(trans-L)] + complexes (NN = bidentate polypyridyl ligands and trans-L = stilbene-like ligand), which find use in molecular machines and photosensors, are discussed. Finally, dye-sensitized energy conversion devices based on Ru II complexes and natural dyes, such as dye-sensitized solar cells (DSCs) and dye-sensitized photoelectrosynthesis cells (DSPECs), are reviewed, highlighting some strategies for photoanode engineering aiming at improved device efficiencies.

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The preparation of nanostructured thin films consisted of TiO 2 / ZnO bilayers (BL) and their application in dye-sensitized solar cells (DSCs) are reported. The film was prepared by the Layerby-Layer (LbL) technique using, respectively, acid and basic sols of TiO 2 and ZnO nanoparticles. The particles in the sols were characterized by dynamic light scattering (DLS) and the compact morphology of the LbL films were probed by scanning electronic (SEM) and atomic force (AFM) microscopies. The photoelectrochemical parameters of DSCs with 0, 15 and 20 BL were assessed by current-voltage (JxV) curves, incident photon-to-current efficiency (IPCE), electron lifetime and electrochemical impedance spectroscopy (EIS). These results revealed a significant improvement (up to 67%) on the DSC conversion efficiency promoted by LbL film underlayers, with enhancements ascribed to an efficient blocking effect preventing the FTO/I 3 À charge recombination and improved contact between the mesoporous-TiO 2 and the conducting substrate (FTO).