Electronic and Spectroscopic Properties of Avobenzone Derivatives Attached to Ditungsten Quadruple Bonds

From the reactions between W2(TiPB)4, where TiPB is 2,4,6-triisopropylbenzoate, and 2 equiv of acid, 4-formylbenzoic acid, HBzald, 4-(3-oxo-3-phenylpropanoyl)benzoic acid, HAvo, or 4-(2,2-difluoro-6-phenyl-2H-1λ3,3,2λ4-dioxaborinin-4-yl)benzoic acid, HAvoBF2, three new compounds W2(TiPB)2(Bzald)2, I, W2(TiPB)2(Avo)2, II, and W2(TiPB)2(AvoBF2)2, III, have been prepared. As solid compounds I and II are blue while compound III is green. Characterization of these compounds has been carried out by means of 1H NMR, MALDI-TOF MS, steady-state absorption and emission spectroscopies, and femtosecond and nanosecond transient absorption and time-resolved infrared spectroscopies. Compounds I and II have strong metal to ligand charge transfer, MLCT, transitions in the visible region of their spectra while compound III exhibits MLCT absorption in the near-infrared (λmax = 1017 nm). All three have S1 states that have corresponding lifetimes of ∼3–30 ps and are 1MLCT in character. The triplet states are 3MLCT with lifeti...