Third-Generation W(CNAr)6 Photoreductants (CNAr = Fused-Ring and Alkynyl-Bridged Arylisocyanides)

Homoleptic tungsten(0) arylisocyanides possess photophysical and photochemical properties that rival those of archetypal ruthenium(II) and iridium(III) polypyridine complexes. Previous studies established that extending the π-system of 2,6-diisopropylphenylisocyanide (CNDipp) by coupling aryl substituents para o the isocyanide functionality results in W(CNDippAr) 6 oligoarylisocyanide complexes with greatly enhanced metal-to-ligand charge transfer (MLCT) excited-state properties relative to those of W(CNDipp) 6 . Extending electronic modifications to delineate additional design principles for this class of photosensitizers, herein we report a series of W(CNAr) 6 compounds with naphthalene-based fused-ring (CN-1-(2- i Pr)-Naph) and CNDipp-based alkynyl-bridged (CNDipp CC Ar) arylisocyanide ligands. Systematic variation of the secondary aromatic system in the CNDipp CC Ar platform provides a straightforward method to modulate the photophysical properties of W(CNDipp CC Ar) 6 complexes, allowing access to an extended range of absorption/luminescence profiles and highly reducing excited states, while maintaining the high molar absorptivity MLCT absorption bands, high photoluminescence quantum yields, and long excited-state lifetimes of previous W(CNAr) 6 complexes. Notably, W(CN-1-(2- i Pr)-Naph) 6 exhibits the longest excited-state lifetime of all W(CNAr) 6 complexes explored thus far, highlighting the potential benefits of utilizing fused-ring arylisocyanide ligands in the construction of tungsten(0) photoreductants.