Thiophene-Fused Nickel Dithiolenes: A Synthetic Scaffold for Highly Delocalized π-Electron Systems

A series of thiophene-fused nickel dithiolene complexes have been prepared via synthetic methods which allow the addition of peripheral aryl groups to the fused thiophene of the dithiolene ligand, thus providing access to a range of structural and electronic modifications to the dithiolene core. X-ray structural studies of the anionic complexes show that the peripheral aryl rings lie in near-perfect coplanarity to the dithiolene core and can form π-stacked columns with N-methylpyridinium cations. Density functional theory calculations show significant delocalization of the frontier orbital electron density into the peripheral aryl rings. The complexes exhibit tunable, intense near-IR (NIR) absorption in the range of 1076-1160 nm with molar absorptivity as high as 25100 M^-1 cm^-1 in solution. The electronic tunability as well as the desirable solid-state packing arrangements of these systems suggests significant potential as NIR-absorbing materials for optoelectronic applications.