Photophysical properties of cis-Mo2 quadruply bonded complexes and observation of photoinduced electron transfer to titanium dioxide.

The compounds cis-Mo2(DAniF)2(L)2 have been prepared, where DAniF = (N,N′)-p-dianisyl formamidinate and L = thienyl-2-carboxylate (Th), 2,2′-bithienyl-5-carboxylate (BTh), and 2,2′:5′,5″-terthienyl-5-carboxylate (TTh). The compounds have been characterized by proton nuclear magnetic resonance (1H NMR), ultraviolet–visible (UV–vis) absorption and emission, differential pulse voltammetry, and time-resolved transient absorption and infrared (IR) spectroscopy. An X-ray crystal structure was obtained for the thienyl complex. The related salt [nBu4N]2[Mo2(DAniF)2(TTh–CO2)2], where TTh–CO2 = 2,2′:5′,2″-terthienyl-5,5″-dicarboxylate, has also been prepared and employed in the attachment of the complex to TiO2 nanoparticles. The latter have been characterized by ground-state Fourier transform infrared spectroscopy (FTIR) and femtosecond time-resolved IR spectroscopy. The time-resolved data provide evidence for sub-picosecond charge injection from the Mo2 center to the semiconducting oxide particle.