Multistimuli-Responsive Properties of Aggregated Isocyanide Cycloplatinated(II) Complexes

Abstract

Here, we describe the neutral cyclometalated tert-butylisocyanide PtII complexes, [Pt(C∧N)Cl(CNBut)] 1, the double salts [Pt(C∧N)(CNBut)2][Pt(C∧N)Cl2] 2, and the cationic complexes [Pt(C∧N)(CNBut)2]ClO43 [C∧N = difluorophenylpyridine (dfppy, a), 4-(2-pyridyl)benzaldehyde (ppy-CHO, b)]. A comparative study of the pseudopolymorphs 1a, 1a·CHCl3, 1b, 1b·0.5Toluene, 1b·0.5PhF, and 3a·0.25CH2Cl2 reveals strong aggregation through Pt···Pt and/or π···π stacking interactions to give a variety of distinctive one-dimensional (1D) infinite chains, which modulate the photoluminescent properties. This intermolecular long-range aggregate formation is the main origin of the photoluminescent behavior of 1a and 1b complexes, which exhibit highly sensitive and reversible responses to multiple external stimuli including different volatile organic compounds (VOCs), solvents, temperatures, and pressures, with distinct color and phosphorescent color switching from green to red. Furthermore, complex 1b undergoes supramolecular self-assembly via Pt···Pt and/or π···π interactions into a polymer thin polystyrene (PS) film 10 wt % in response to toluene vapors, and 3a exhibits vapochromic and vapoluminescent behavior. Theoretical simulations on the dimer, trimer, and tetramer models of 1a and 1b have been carried out to get insight into the photophysical properties in the aggregated solid state.