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 pi-system of 2,6-diisopropylphenylisocyanide (CNDipp) by coupling aryl substituents para to 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-Pr-i)-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-Pr-i)-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.