Solid state structure and photophysical properties of monoanionic 2-(2′-hydroxyphenyl)benzimidazole as an anionic core in rhenium complex

Abstract

A monoanionic 2-(2′-phenolate)benzimidazole (HPBI−) stabilized in organometallic complex [Re(CO)2 (dppe)2](HPBI) (1) which was obtained by treating 2-(2′-hydroxyphenyl)benzimidazole (H2–PBI), 1,2-bis(diphenylphosphino)ethane (dppe), and Re2(CO)10, in toluene using a one-pot approach. Solid state structure of complex was determined using a single crystal X-ray diffraction analysis. The monoanionic HPBI− in 1 is nearly planar and adopts trans-anion conformation i.e., both oxygen atom and NH proton are on the same side and are stabilized by the intramolecular N–H⋅⋅⋅O hydrogen bonding interaction. The photophysical properties of 1 in solution are corroborated with the monoanionic HPBI− anion generated in situ from neutral H2PBI by adding base. The solid state emission of 1 is red-shifted in compared to that of 1 in the solution. The monoanionic HPBI− in 1 was transformed into dianionic PBI2− in the complex, {[Re(CO)2 (dppe)2](HPBI) (1) → (Bu4N)[Re(CO)2 (dppe)2](PBI) (2)}, by adding tetrabutylammonium fluoride (Bu4NF) without decomposing the coordination complex.