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

Abstract

Here, we describe the neutral cyclometalated <i>tert-</i>butylisocyanide Pt^II complexes, [Pt(C^∧N)Cl(CNBu<i>^t</i>)] <b>1</b>, the double salts [Pt(C^∧N)(CNBu<i>^t</i>)₂][Pt(C^∧N)Cl₂] <b>2</b>, and the cationic complexes [Pt(C^∧N)(CNBu<i>^t</i>)₂]ClO₄ <b>3</b> [C∧N = difluorophenylpyridine (dfppy, <b>a</b>), 4-(2-pyridyl)benzaldehyde (ppy-CHO, <b>b</b>)]. A comparative study of the pseudopolymorphs <b>1a</b>, <b>1a·CHCl</b>_<b>3</b>, <b>1b</b>, <b>1b·0.5Toluene</b>, <b>1b·0.5PhF</b>, and <b>3a·0.25CH</b>_<b>2</b><b>Cl</b>_<b>2</b> 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 <b>1a</b> and <b>1b</b> 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 <b>1b</b> undergoes supramolecular self-assembly <i>via</i> Pt···Pt and/or π···π interactions into a polymer thin polystyrene (PS) film 10 wt % in response to toluene vapors, and <b>3a</b> exhibits vapochromic and vapoluminescent behavior. Theoretical simulations on the dimer, trimer, and tetramer models of <b>1a</b> and <b>1b</b> have been carried out to get insight into the photophysical properties in the aggregated solid state.