Vapochromism and Its Structural Basis in a Luminescent Pt(II) Terpyridine−Nicotinamide Complex

Abstract

A novel Pt(II) terpyridine complex that has a nicotinamide moiety linked to the terpyridyl ligand has been synthesized in good yield and studied structurally and spectroscopically. The complex, [Pt(Nttpy)Cl](PF(6))(2) where Nttpy = 4'-(p-nicotinamide-N-methylphenyl)-2,2':6',2' '-terpyridine, is observed to be brightly luminescent in the solid state at room temperature and at 77 K. The complex exhibits reversible vapochromic behavior and crystallographic change in the presence of several volatile organic solvents. Upon exposure to methanol vapors, the complex changes color from red to orange, and a shift to higher energy is observed in the emission maximum with an increase in excited-state lifetime and emission intensity. The crystal and molecular structures of the orange and red forms, determined by single-crystal X-ray diffraction on the same single crystal, were found to be equivalent in the molecular sense and only modestly different in terms of packing. In both forms, the cationic Pt(II) complexes possess distorted square planar geometries. Analysis of the orange form's crystal packing reveals the presence of solvent molecules in lattice voids, Pt...Pt separations averaging 3.75 A and a zigzag arrangement between nearest neighbor Pt atoms, whereas the red form is devoid of solvent within the crystal lattice and contains complexes stacked with a nearly linear arrangement of Pt(II) ions having an average distance of 3.33 A. On the basis of the crystallographic data, it is evident that sorption of methanol vapor induces a change in intermolecular contacts and Pt...Pt interactions in going from red to orange. Disruption of the d(8)-d(8) metallophilic interactions consequently alters the emitting state from (3)[(d)sigma*-pi*(terpyridine)] that is formally a metal-metal-to-ligand charge transfer (MMLCT) state in the red form to one in which the HOMO corresponds to a more localized Pt(d) orbital in the red form ((3)MLCT).

Transformation of a CuII Thiazolo‐1,2,4‐triazine Derivative from a Metastable Coordination Network to a Monomer in Solution and Vapor Conditions

“…Generally, the vapochromism is mainly induced due to two reasons: (i) a coordination exchange reaction between the metal and the solvents [15][16][17][18] and (ii) a change in the crystal packing due to inclusion of solvents. [19][20][21][22][23][24][25] In this case, we suggest that a dynamic disproportionation reaction of 5a (CuCl 2 /3a = 1:1) occurred and produced a new aggregation state composed of the mononuclear complex 6a (CuCl 2 /3a = 1:2) and the solvated metal ion in the solid. The orange-yellow powder 5a is stable in a dry atmosphere after isolation from the solvent.…”

Metal‐Containing Polymers: Building Blocks for Functional (Nano)Materials

“…This structural dynamism often leads to stimuli responsive magnetic or optical property changes, and is useful for the development of smart materials for uses in sensors, selective gas absorbents and separation science. [53,[55][56][57] Often stemming from the formation and deformation of weak interactions, such as coordinative bonds, hydrogen bonds, stacking etc, [58,59] dynamic structural transformation can be classified into two categories: 1) guest-induced crystal-to-amorphous transformation, which leads to a reversible collapse and regeneration of the framework; [60] 2) guest-induced crystalto-crystal transformation, in which two crystalline structures reversibly form depending on their interaction with guest molecules. [61][62][63] In addition to coordination chemistry transformations, ligands containing a highly flexible component offer another possibility for varying porosity after MOF formation.…”

Luminescent detection of the lipopolysaccharide endotoxin and rapid discrimination of bacterial pathogens using cationic platinum(ii) complexes

“…20 These complexes have attracted much attention due to their luminescence properties and their potential applications in chemical sensing and biosensing. [21][22][23][24] For example, an alkynylplatinum(II) terpyridine complex has been reported to detect human serum albumin (HSA). 22 Cl] + (70.1 mM) and LPS (3.0 mM) was transferred into a cuvette, and the particle size was measured at room temperature.…”