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

Javier Fajardo Jr; Josef Schwan; Wesley W Kramer; Michael K Takase; Jay R Winkler; Harry B Gray

doi:10.1021/acs.inorgchem.0c02912

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

Inorg Chem. 2021 Mar 15;60(6):3481-3491. doi: 10.1021/acs.inorgchem.0c02912. Epub 2020 Dec 6.

Authors

Javier Fajardo Jr¹, Josef Schwan¹, Wesley W Kramer¹, Michael K Takase¹, Jay R Winkler¹, Harry B Gray¹

Affiliation

¹ Beckman Institute, California Institute of Technology (Caltech), Pasadena, California 91125, United States.

PMID: 33280385
DOI: 10.1021/acs.inorgchem.0c02912

Abstract

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 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-ⁱPr)-Naph) and CNDipp-based alkynyl-bridged (CNDipp^CCAr) arylisocyanide ligands. Systematic variation of the secondary aromatic system in the CNDipp^CCAr platform provides a straightforward method to modulate the photophysical properties of W(CNDipp^CCAr)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-ⁱPr)-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.