Acetonitrile-Vapor-Induced Color and Luminescence Changes in a Cyclometalated Heteroleptic Iridium Complex

Abstract

An iridium complex PIr(qnx) (iridium(III) bis(2-phenylpyridinato-N,C(2))(quinoxaline-2-carboxylate)) is reported for its unique and fast vapochromic and vapoluminescent behaviors. The emission of PIr(qnx) is governed by the whole crystal rather than the individual molecule. PIr(qnx) has been found to exist as both black and red forms in the solid state. The black form can be transformed into the red form upon its exposure to acetonitrile or propiononitrile vapor, whereas no response was observed when it was exposed to other volatile organic compounds. To understand the vapochromic and vapoluminescent behaviors, we determined crystal structures of both forms by X-ray diffraction. In addition, we employed density functional theory in investigating weak intermolecular interactions, such as hydrogen bonding and pi-pi interactions in the two forms.

Functional IrIII Complexes and Their Applications

“…[4][5][6] Thus, Ir III complexes have been widely studied for many applications including organic light-emitting diodes (OLEDs), [7][8][9][10][11] light-emitting electrochemical cells (LECs), [12] luminescence sensitizers, [13,14] biological labeling, [15,16] and chemosensors. [16][17][18][19][20][21] In pursuit of a highly emissive Ir III complex, many heteroleptic complexes of the type [Ir(C^N) 2 MLCT transitions. In such cases, density functional theory calculations indicate that the highest occupied molecular orbital (HOMO) is largely metal-centered, whereas the lowest unoccupied molecular orbital (LUMO) is primarily localized on the heterocyclic rings of the cyclometalated ligands.…”

Laser Spectroscopy for Atmospheric and Environmental Sensing

“…Liu et al [361] reported a vapoluminescent cyclometalated heteroleptic iridium complex [iridium(III)-bis(2-phenylpyridinato-N,C2)(quinoxaline-2-carboxylate); PIr(qnx)] that was synthesized into two forms (black and red forms). The black form is weakly luminescent at 692 nm, with a short lifetime of 43 ns.…”

“…Photoluminescence spectra of the black form exposed to acetonitrile vapor at different periods of time. Reproduced with permission from [361]. …”

Chromo- and Fluorogenic Organometallic Sensors

“…10) shows selective vapochromic and vapoluminescent properties in response to acetonitrile or propiononitrile vapour, while remaining unchanged for other VOCs [105]. Crystals of the compound change from a black to a red polymorph in less than 1 min on exposure to the solvent vapours; at the same time, strong emission is switched 'on' (red form).…”