Temperature-dependent photoluminescence down to 77 K of organotin molecular rotors: eco-friendly synthesis, photophysical characterization, X-ray structures, and DFT studies

Fluorescent organotin compounds are useful in sensing, optoelectronic devices, and in vitro bioimaging. Although in vitro fluorescence bioimaging shows low resolution at room temperature, a better resolution is possible at cryotemperatures. Therefore, the search for new cryoluminescent materials with potential application in high-resolution fluorescence bioimaging remains a great challenge. Herein, we report the cryoluminescence properties of two fluorescent bis-organotin compounds, namely, BisNTHySnBu2 (5) and BisNTHySnPh2 (6), synthesized via microwave irradiation. All compounds were fully characterized using 1H, 13C, and 119Sn NMR spectroscopy, Raman spectroscopy, IR spectroscopy, and HR-MS. The 119Sn δ and 3J(1H,119Sn) of 5 and 6 indicate that two Sn-ligands are chemically and electronically equivalent, as confirmed by cyclic voltammetry. The crystal structure of 6 showed pentacoordinate tin atoms with skeleton ligands. The study of self-assembled monolayers of both Sn-complexes via STM microscopy revealed a similar supramolecular packing in lamella-like patterns, adopting a face-on arrangement, where molecules stay flat lying on HOPG in accordance with the height profile of closely packed monolayers on graphite of about 0.33 nm thickness. However, only the Sn complex 6, which bears phenyls, covers large surface areas. The photophysical properties of bis-organotin compounds were also investigated in solution (room and low temperatures) and in the solid state. Good luminescence properties in solutions with fluorescence quantum yields (Φ) of approximately 35% and 50% were found. Despite this, Φ is quenched in the solid state because of aggregation, as supported by solvent/non solvent fluorescence studies, which is in agreement with STM and AFM investigation.

Synthesis of M-UiO-66 (M = Zr, Ce or Hf) employing 2,5-pyridinedicarboxylic acid as a linker: defect chemistry, framework hydrophilisation and sorption properties

MOFs of general composition [M₆(OH)₄(O)₄(PDC)_6−x(Cl)_2x(H₂O)_2x] with M = Zr, Ce, Hf; and 0 ≤ x ≤ 2 were obtained and characterised in detail.

Site-selective Eu(iii) spectroscopy of highly efficient luminescent mixed-metal Pb(ii)/Eu(iii) coordination polymers

Novel coordination polymers based on Pb_1−xEu_x–BDC (x = 0.05–0.50, BDC = 1,4-benzenedicarboxylic acid) are reported with a maximum emission quantum yield of 69 ± 7%.

Synthesis and structure of Zr(iv)- and Ce(iv)-based CAU-24 with 1,2,4,5-tetrakis(4-carboxyphenyl)benzene

Eight-fold connection of hexanuclear clusters containing Zr(iv) or Ce(iv) through rigid, rectangular tetracarboxylate ions yields new MOFs with scu topology.

Unique anisotropic optical properties of a highly stable metal–organic framework based on trinuclear iron(iii) secondary building units linked by tetracarboxylic linkers with an anthracene core

A highly stable metal–organic framework, [{Fe₃(ACTBA)₂}X·6DEF]_n (1; X = monoanion), is reported.

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.