Dual stimuli-responsive phosphorescence of a Pb(II) coordination polymer to acidic vapors and thermal treatment.

We present a new intensely phosphorescent Pb(II) coordination polymer (1) containing a heteroatomic ligand. It has a quantum yield of 21.62% and a lifetime of 25.46 µs. The naked-eye solid-state photoluminescence of 1 significantly changes in response to acidic vapors and thermal treatment, indicating the coexistence of acidochromic and thermochromic luminescence.

Simultaneous Occurrence of Vapochromism and Vapoluminescence in Formaldehyde-Responsive Amino-Functionalized Copper(I) Polymorphic Coordination Polymers.

The use of vapor-responsive chromic materials in sensing applications for the detection of harmful volatile organic chemicals is rapidly expanding. Herein, four new amino-functionalized Cu(I) coordination polymers of [CuI(pyt-NH2)]n (1) and (2) and [CuSCN(pyt-NH2)]n (3) and (4) (where pyt-NH2 = 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole) were successfully synthesized. Single-crystal X-ray diffraction analysis reveals that 1 and 2 are iodo-based polymorphs, while 3 and 4 are thiocyanato-based polymorphs. They possess densely diverse crystalline architectures decorated by uncoordinated amino groups as a binding site. Also, 1-4 show a variety of color and luminescence based on the structural diversity. Remarkably, 1 and 2 undergo the change of color and naked-eye solid-state luminescence in response to formaldehyde (FA) vapor, demonstrating simultaneous vapochromism and vapoluminescence. The chromic Cu(I) coordination polymers in this work present for the first time dual-mode vapochromism and vapoluminescence in a highly selective response to FA vapor. The responsive mechanism has been clarified by Fourier transform infrared spectroscopy (FT-IR), electrospray ionization mass spectrometry (ESI-MS), 1H nuclear magnetic resonance (NMR), powder X-ray diffraction (PXRD), and luminescence lifetime measurements, which reveal carbinolamine formation via the specific reaction between FA and the active amino groups of coordinated pyt-NH2. The carbinolamine formation can trigger the structural transformation of 1 and 2, leading to the concurrently selective vapochromism and vapoluminescence induced by FA vapor.

Coexistence of Naked-Eye Mechanochromism, Vapochromism, and Thermochromism in a Soft Crystalline Layered Nickel(II) Coordination Polymer.

Chromic materials have the potential to be used in a variety of applications, including memory devices and sensors. Despite fact that stimuli-responsive chromic materials have been widely reported to date, fabricating chromic materials that can be responsive to multiple external stimuli remains a challenge. Herein, a new multistimuli responsive chromic coordination polymer of {[Ni(pzt)2(H2O)2](H2O)(DMF)}n (1); Hpzt = 5-(3-pyridyl)-1,3,4-oxadiazole-2-thiol, was successfully synthesized. Single-crystal X-ray diffraction analysis revealed that 1 exhibits a soft crystalline 3-dimenional (3D) supramolecular framework generated by weakly interlayered stacking interactions between 2D coordination polymers. Compound 1 revealed unprecedented naked-eye mechanochromism, vapochromism, and thermochromism in response to multiple external stimuli including manual grinding, amine and alcohol vapors, and heat, respectively. The chromism related to the structural feature was clarified by SC-XRD, PXRD, TGA, elemental analysis, and spectroscopic techniques.

A Solid-State Luminescent Cd(II) Supramolecular Coordination Framework Based on Mixed Luminophores as a Sensor for Discriminatively Selective Detection of Amine Vapors.

A novel Cd(II) supramolecular coordination framework containing mixed functionalized luminophore ligands, namely, [Cd(AS)2(phen)2]EtOH or 1 (where AS = 4-aminosalicylate, phen = 1,10-phenanthroline, EtOH = ethanol), was successfully synthesized as a solid-state luminescent sensor for the detection of amine vapors. The single-crystal X-ray diffraction analysis revealed that 1 possesses a three-dimensional (3D) supramolecular framework enclosing ethanol molecule in the lattice. The supramolecular structure is well-stabilized by various noncovalent intermolecular interactions through functional groups of ligands. Compound 1 shows an intense yellow solid-state emission and displays a reversibly discriminative luminescent response to NH3 and ethylenediamine (EDA) vapors through very large blue-shifted luminescent spectra with distinguishable emission colors under UV light. This work reports the first time for selective luminescent sensing of NH3 and EDA vapors with considerably different emission color change. A sensing mechanism has been confirmed by density functional theory and time-dependent density functional theory calculations that agrees well with the experimental results. Also, 1 exhibits a good recyclability over five cycles for sensing of NH3 and EDA vapors.