A Mechanochromic and Vapochromic Luminescent Cuprous Complex Based on a Switchable Intramolecular π···π Interaction

Abstract

An in-depth study on a stimuli-responsive tetranuclear cuprous luminescent complex is reported and gives new insights into the origin and possible use of the observed stimuli-responsive luminescence. Its crystalline polymorphs with two different shapes are obtained by using different crystallization solvents and show distinct emissions, with one being blue emissive and the other being yellow emissive. Upon grinding, only the blue-emitting polymorph has a marked change in the emission color from blue to yellow, and its ground sample exhibits a yellow emission similar to that of the yellow-emitting polymorph. Interestingly, the yellow-emitting polymorph after exposure to acetone vapor can emit a blue emission and display luminescence mechanochromism similar to that of the blue-emitting polymorph. Single-crystal structural analyses of the two different polymorphs reveal the relationship between the mechanochromic luminescence and the geometrical configuration of the {Cu­(μ-dppm)2Cu} unit and intramolecular “pyridyl/phenyl” π···π interactions, supported as well by their PXRD, FT-IR, TGA, and PL studies in various states and by TD-DFT analyses. The results demonstrate the different roles of switchable intramolecular π···π interactions and the geometrical configuration of the {Cu­(μ-dppm)2Cu} unit in this stimuli-responsive luminescence and potential applications of such stimuli-responsive luminescence in optical sensing and anticounterfeiting encryption technologies and deepen the understanding of such stimuli-responsive luminescence originating from switchable intramolecular π···π interactions. In addition, it is clearly suggested that the rational utilization of switchable intramolecular π···π interactions is a feasible route for developing stimuli-responsive intelligent luminescent materials and devices.

Mechanochromic and Selective Vapochromic Solid-State Luminescence of a Dinuclear Cuprous Complex

“…35−40 NHbearing diimine ligands are suitable for the design and synthesis of multi-stimuli-responsive luminescent materials based on cuprous complexes since they usually tend to generate hydrogen bonds with surrounding molecules and ions via the N−H functional groups 35,36,41 and form intramolecular π•••π interactions with phenyl rings of coordinated phosphine ligands. 25,27,42 Herein, we report two different solvated polymorphs, 1• 2CH 2 Cl 2 (1-g) and 1•2CHCl 3 (1-c), derived from the new dinuclear cuprous complex [{Cu(bpmtzH)} 2 (μ-dppm) 2 ]-(ClO 4 ) 2 (1) (Figure 1a). The two differently emissive polymorphs 1-g and 1-c exhibit mechanochromic and selective vapochromic solid-state photoluminescence properties, mainly attributable to the breakage of NH a CH 2 Cl 2 solution.…”

Thermo-, Mechano-, and Vapochromic Dinuclear Cuprous-Emissive Complexes with a Switchable CH3CN–Cu Bond

“…Generally, the luminescence of materials is relevant to changes in noncovalent interactions, such as hydrogen-bonding and π···π interactions. − Modulation of noncovalent interactions often leads to the change of molecular packing and the occurrence of phase transition. − For metal complexes, the coordination geometry of metal ions has an important influence on the luminescence and is closely related to the change of coordination bonds. − Therefore, the construction of switchable weak coordination is a feasible approach to regulate the coordination geometry conversion and achieve luminescence switching.…”

Multistimuli-responsive behavior of a phosphorescent Cu3pyrazolate3complex for luminescent logic gates and encrypted information transformation

“…27 To date, although intriguing multi-responsive complexes based on platinum, gold, or other precious metals have been reported, 26,[28][29][30][31][32] Cu(I) complexes are still very promising candidates for low-cost multi-responsive materials. Examples include a tetranuclear Cu(I) complex showing luminescence mechanochromism and vapochromism triggered by the alternation of intramolecular π⋯π interactions, 33 a dinuclear Cu(I) complex showing luminescence thermo-, mechano-, and vapochromism relevant to a switchable CH 3 CN-Cu bond, 34 and a Cu(I) metal-organic framework for sensing temperature, solvents and nitro explosives. 35 Pyrazolate-based Cu(I) cyclic trinuclear complexes (CTCs) represent an important class in the family of coinage-metalbased CTCs, whose fascinating luminescence behaviors are often dominated by aggregation.…”