Two viologen-based photoluminescent compounds: excitation-wavelength-dependent and photoirradiation-time-dependent photoluminescent switches

We synthesized two isostructural multi-coloured photoluminescent coordination polymers. They exhibit excitation-wavelength-dependent photoluminescence emission and photoirradiation-time-dependent photoluminescence emission in solid-state.

New photoluminescent iodoargentates with bisimidazole derivatives as countercations

In this article, three bisimidazole derivatives (1,4-bis(2-ethylimidazol-1-yl)butane, L1; 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl, L2′; and 1,3-bis(2-ethylimidazol-1-yl)propane, L3) were employed to solvothermally react with AgI in an acidic environment, creating three new 1-D chained iodoargentates [H(L1)][Ag₅I₆]·DMF (DMF = N,N′-dimethylformamide) 1, [L2][Ag₃I₅] (L2²⁺ = 4,4′-di(1H-imidazol-1-ium)-1,1′-biphenyl) 2, and [H₂(L3)][Ag₂I₄] 3. L2²⁺ in 2 originated from the in situ N-alkylation of L2′ with the CH₃OH solvent. X-ray single-crystal diffraction analysis reveals that (i) in 1, Ag⁺ and I⁻ aggregate to form a 1-D tube-like iodoargentate, which exhibits the same topology as the carbon tube; (ii) the chain structure of the iodoargentate in 2 is based on a kind of trinuclear Ag–I cluster, which can be viewed as a segment of the classical cubic M₄I₄ cluster; (iii) the chain structure of the iodoargentate in 3 is simple, which can be described as a linear arrangement of the AgI₄ tetrahedra by sharing edges. The photoluminescence analysis reveals that at 77 K, (i) 1 and 2 emit strong yellow light with ms-grade photoluminescence lifetimes (5.460 ms for 1, 6.931 ms for 2); (ii) 3 possesses photochromic luminescence properties. Upon excitation at 254 nm, it emits blue-green light, whereas upon excitation at 365 nm, it emits yellow light.

Three bisimidazole-based chained iodoargentates were solvothermally synthesized, and their photoluminescent behaviors at different temperatures were investigated. Of those, 3 has been found to possess photochromic luminescence properties.

New organically templated thiocyanatocadmates and chlorocuprate(II): synthesis and structural characterization

With various organic base molecules as the countercations, five new thiocyanatocadmates [H2(tmen)][Cd(SCN)4] (tmen = N,N,N',N'-tetramethylethylenediamine) 1, [H2(tmba)][Cd2(SCN)6] (tmba = N,N,N',N'-tetramethyl-1,4-butanediamine) 2, [H2(teen)][Cd2(SCN)6] (teen = N,N,N',N'-tetra-ethylethylenediamine) 3, [H(amp)][Cd(SCN)2(CH3COO)] (amp = 2-amino-6-methylpyridine) 4 and [H(abp)]4[Cd(SCN)4]SO4·H2O (abp = 2-amino-6-bromopyridine) 5, and one new chlorocuprate(II) [H2(cha)][CuCl4] (cha = 1,4-cyclohexanediamine) 6 were obtained from a series of simple room-temperature self-assemblies at pH = 2 or 6.5. X-ray single-crystal diffraction analysis reveals that (i) templated by [(CH3)2NH(CH2)2NH(CH3)2](2+) (H2(tmen)(2+)), the anion [Cd(SCN)4](2-) in 1 shows a 1-D linear single-chain structure, whereas templated by [(CH3)2NH(CH2)4NH(CH3)2](2+) (H2(tmba)(2+)), the anion [Cd2(SCN)6](2-) in 2 shows a 1-D linear double-chain structure. The number of C atoms between the two N atoms in the templating agent controls the width of the anionic chain through the N(amino)-H···N(SCN) interactions; (ii) templated by [(C2H5)2NH(CH2)2NH(C2H5)2](2+) (H2(teen)(2+)), the anion [Cd2(SCN)6](2-) in 3 exhibits a 3-D open-framework structure, which is based on zigzag anionic chains. A direct change of the substituent group from -CH3 to -C2H5 alters indirectly the shape of the anionic chain from a linear shape to a zigzag shape; (iii) 4 shows a 3-D supramolecular network structure, which is built up from the 1-D zigzag anionic structures by the H(amp)(+) molecules via N-H···O interactions. The formation of the zigzag chain derives from the chelation of the CH3COO(-) groups to the Cd(2+) centers; (iv) 5 is indeed a double salt of [H(abp)]2[Cd(SCN)4] and [H(abp)]2SO4. SO4(2-) and H(abp)(+) form a supramolecular aggregation. Surrounded by the aggregations, the anion [Cd(SCN)4](2-) only shows a dinuclear structure; and (v) templated by H2(cha)(2+), the anion [CuCl4](2-) in 6 displays a 2-D perovskite layer structure. The photoluminescence analysis indicates that upon excitation (λ(ex) = 335 nm for 4, λ(ex) = 395 nm for 5), and emit light (λ(em) = 365 nm for 4, λ(em) = 470 nm for 5), which can be seen clearly under the UV lamp.

A 3-D metal–organic framework with a rutile topology network, right- or left- handed helical chains and tunable UV-to-visible photoluminescence

A solvothermally synthesized 3-D Cd(ii) metal–organic framework with rutile topology was found containing right- or left- handed helices in its structure, and emitting tunable UV-to-visible photoluminescence.

Color tunable and near white-light emission of two solvent-induced 2D lead(ii) coordination networks based on a rigid ligand 1-tetrazole-4-imidazole-benzene

Two solvent-induced Pb(ii)-tzib⁻ (Htzib = 1-tetrazole-4-imidazole-benzene) coordination polymers display color tunable and near white-light emissions upon varying excitation wavelengths.