Bespoke Photoreductants: Tungsten Arylisocyanides

Modular
syntheses of oligoarylisocyanide ligands that are derivatives
of 2,6-diisopropylphenyl isocyanide (CNdipp) have been developed;
tungsten complexes incorporating these oligoarylisocyanide ligands
exhibit intense metal-to-ligand charge-transfer visible absorptions
that are red-shifted and more intense than those of the parent W­(CNdipp)6 complex. Additionally, these W­(CNAr)6 complexes
have enhanced excited-state properties, including longer lifetimes
and very high quantum yields. The decay kinetics of electronically
excited W­(CNAr)6 complexes (*W­(CNAr)6) show
solvent dependences; faster decay is observed in higher dielectric
solvents. *W­(CNAr)6 lifetimes are temperature dependent,
suggestive of a strong coupling nonradiative decay mechanism that
promotes repopulation of the ground state. Notably, *W­(CNAr)6 complexes are exceptionally strong reductants: [W­(CNAr)6]+/*W­(CNAr)6 potentials are more negative than
−2.7 V vs [Cp2Fe]+/Cp2Fe.