Polymeric copper(I)-NHC complexes with bulky bidentate (N

Starting from imidazolium chlorides bearing bulky nitrogen donors, a series of four complexes, mainly [Cu(C^N)Cl]n coordination polymers were obtained directly as luminescent species by simple filtration from the aqueous reaction medium, highlighting a simple, eco-friendly, robust and reproducible synthetic procedure. Additionally, we have shown on the most efficient example that chloride could be exchanged very easily by other halides/pseudohalides (Br-, I-, NCS-, N3-) allowing to slightly modulate the emitted colour while conserving the polymeric structure, except for azide for which a dimer was obtained. The combination of chemical analyses, of photoluminescence studies in the solid state including quantum yield measurement and X-ray diffraction on single crystals and as-synthesized microcrystalline powders highlighted that the polymeric luminescent species was indeed obtained directly by simple filtration and that no major alteration of the structure was observed upon recrystallisation. Samples of all polymeric complexes displayed remarkable stability towards air oxidation remaining unchanged upon storage for several months and partially retaining their photoluminescence properties even after a thermal treatment at 100 °C for 24 h.

A gold(I) 1,2,3-triazolylidene complex featuring the interaction between gold and methine hydrogen.

A mesoionic N-heterocyclic carbene-gold(I) complex with a unique Au⋯H-C(methine) intramolecular hydrogen bonding interaction has been investigated in the solid state. The structure of this new neutral gold(I)-carbene was characterized by FT-IR and NMR spectroscopy, TGA, and X-ray diffraction techniques. Density functional theory (DFT) and atoms-in-molecule (AIM) analysis revealed that the gold-hydrogen bonding situation is more favored. Besides, the photophysical properties of the gold(I) complex were also investigated.

Acridine N-Heterocyclic Carbene Gold(I) Compounds: Tuning from Yellow to Blue Luminescence.

The synthesis and the luminescence features of three gold(I)-N-heterocyclic carbene (NHC) complexes are presented to study how the n-alkyl group can influence the luminescence properties in the crystalline state. The mononuclear gold(I)-NHC complexes, [(L1 )Au(Cl)] (1), [(L2 )Au(Cl)] (2), and [(L3 )Au(Cl)] (3) were isolated from the reactions between [(tht)AuCl] and corresponding NHC ligand precursors, [N-(9-acridinyl)-N'-(n-butyl)-imidazolium chloride, (L1 .HCl)], [N-(9-acridinyl)-N'-(n-pentyl)-imidazolium chloride, (L2 .HCl)] and [N-(9-acridinyl)-N'-(n-hexyl)-imidazolium chloride, (L3 .HCl)]. Their single-crystal X-ray analysis reveals the influence of the n-alkyl groups on solid-state packing. A comparison of the luminescence features of 1-3 with n-alkyl substituents is explored. The molecules 1-3 depicted blue emission in the solution state, while the yellow emission (for 1), greenish-yellow emission (for 2), and blue emission (for 3) in the crystalline phase. This paradigm emission shift arises from n-butyl to n-pentyl and n-hexyl in the crystalline state due to the carbon-carbon rotation of the n-alkyl group, which tends to promote unusual solid packing. Hence n-alkyl group adds a novel emission property in the crystalline state. Density Functional Theory and Time-Dependent Density Functional Theory calculations were carried out for monomeric complex, N-(9-acridinyl)-N'-(n-heptyl)imidazole-2-ylidene gold(I) chloride and dimeric complex, N-(9-acridinyl)-N'-(n-heptyl)imidazole-2-ylidene gold(I) chloride to understand the structural and electronic properties.

Luminescent zinc(ii) selone macrocyclic ring.

The synthesis and photophysical properties of macrocyclic Zn(ii) selone molecule have been reported. The structural property of Zn(ii) selone was elucidated using single crystal X-ray diffraction study. The solid-state structure of zinc(ii) selone molecule exhibits a perfect zinc(ii) selone 28 membered ring system with tetra coordination geometry around zinc(ii) center. The zinc(ii) selone ring system can be considered as the largest zinc(ii) ring system known without any non-interacting centered guest moiety. Detailed trends in photophysical as well as thermal properties were probed. In photoluminescence study, the solid-state sample of zinc(ii) selone ring system emits the bluish-yellow color with considerable quantum yields, while the solution state sample of zinc(ii) selone ring system in DMSO emits bluish-yellow. The luminescence lifetime of zinc(ii) selone was measured using standard time-correlated single photon counting (TCSPC) technique.

Blue-emitting acridine-tagged silver(i)-bis-N-heterocyclic carbene.

Herein, the photophysical properties of an acridine derivative of a bis-N-heterocyclic carbene silver complex were investigated. The HOMO and LUMO energy differences between 9-[(N-methyl imidazol-2-ylidene)]acridine and 4,5-bis[(N-methyl-imidazol-2-ylidene)methyl]acridine were theoretically compared. Based on the calculation, the 4,5-bis N-heterocyclic carbene-tethered acridine type of ligand was found to be a potential source for tuning the fluorescent nature of the resultant metal derivatives. Thus, a 4,5-bis N-heterocyclic carbene (NHC)-tethered acridine silver(i) salt was synthesized, and its photophysical properties were investigated. The 4,5-bis[(N-isopropylimidazol-2-ylidene)methyl]acridine silver(i) hexafluorophosphate complex was obtained from the reaction between [4,5-bis{(N-isopropylimidazolium)methyl}acridine] hexafluorophosphate and Ag2O in very good yield; this molecule was characterized by elemental analysis and FTIR, multinuclear (1H and 13C) NMR, UV-Vis, and fluorescence spectroscopic techniques. The molecular structure has been confirmed by single-crystal X-ray diffraction analysis, which has revealed that the complex is a homoleptic mononuclear silver(i) cationic solid. The charge of the Ag(i)-NHC cation is balanced by the hexafluorophosphate anion. The cationic moieties are closely packed in the chair and inverted chair forms where silver(i) possesses a quasi-linear geometry. Moreover, the silver complex provided blue emission from all the three excitations with good fluorescence quantum yield. The fluorescence lifetime of the silver(i) complex has been determined using the time-correlated single photon counting technique. Interestingly, the fluorescence decay pattern and the fluorescence lifetimes of the silver complex are largely different from those of the parent ligand acridine imidazolium salt. Moreover, the theoretical predictions have been found to be in good agreement with the experimental results.

Catalytically active lead(ii)-imidazolium coordination assemblies with diversified lead(ii) coordination geometries.

Five Pb(ii)-imidazolium carboxylate coordination assemblies with novel structural motifs were derived from the reaction between the corresponding flexible, semi flexible or rigid imidazolium carboxylic acid ligands and lead nitrate. The imidazolium linker present in these molecules likely plays a triple role such as the counter ion to balance the metal charge, the ligand being an integral part of the final product and the catalyst facilitating carbon-carbon bond formation reaction. These lead-imidazolium coordination assemblies exhibit, variable chemical and thermal stabilities, as well as catalytic activity. These newly prepared catalysts are highly active towards benzoin condensation reactions with good functional group tolerance.

Bismuth(III)dichalcogenones as highly active catalysts in multiple C-C bond formation reactions.

Thirteen new bismuth(III) dichalcogenone derivatives of triflates and halides were synthesized and structurally characterized. The mono, di, tetra and heptanuclear complexes were isolated with different bismuth(III) coordination environments. These newly isolated bismuth(III)dichalcogenones were characterized by multinuclear NMR, FT-IR, UV-vis, TGA and single crystal X-ray diffraction techniques. These complexes were tested for the synthesis of symmetrical triaryl- or triheteroarylmethanes and the catalysts were found to be highly active. In particular, the selone complexes were relatively more active than thione complexes. Subsequently, the scope of the catalytic reactions was further explored with different substituents.

Rhenium(I)-based Double-heterostranded Helicates.

Rhenium(I)-based supramolecular coordination complexes were obtained using Re2(CO)10, (2-hydroxyphenyl)benzimidazole-derived bis-chelating N∩O donors and a benzimidazolyl-derived ditopic monodentate N-donor possessing Troger's base spacer in a one-pot approach.

Luminescent imidazolium carboxylate supported aggregate and infinite coordination networks of copper and zinc.

The new copper dimer [LCu(DMF)]2(NO3)4(H2O)(DMF)2 (4), where L = [{1,1'-(CH2)2-C14H8)-3,3'-(CH2CO2)2}{(HCN)2CH}], and porous coordination polymers [{L2Cu(OH2)2}2Br2]x (5) and [{L2Zn(OH2)2}2Br2]x (6) have been isolated from reactions of luminescent imidazolium carboxylate ligand, LH2Br2 (3) and the corresponding metal precursors. The reaction between Cu(NO3)2·3H2O and LH2Br2 (3) in DMF at 100 °C yielded bluish green crystals of tetracationic discrete copper dimer 4, the structure of which contains a rare tetracationic [(DMF)Cu(ii)]2 dimer unit that is bridged by four carboxylates of two L in a "paddle-wheel" structure. When the reaction was carried out in the presence of a water-ethanol-methanol mixture, light green crystals of 5 were obtained. Molecule 5 comprises two-dimensional (2D) porous coordination polymeric sheets consisting of unique symmetrical dinuclear [(C(O)O)Cu(OH2)2(O(O)C)2]2 building blocks, which are connected by imidazolium anthracene spacers. The infinite 2D porous coordination polymeric sheets are further linked by significant intermolecular hydrogen-bonding interactions by bromide anions to form a three-dimensional supramolecular framework. Interestingly, the reaction between zinc dust and LH2Br2 (3) in H2O at room temperature gave similar structural features to those in 5, though they differ in terms of C-O bond distances and M-O-C angles. The solution-state UV-visible absorption spectra of 2-6 in water exhibits the comparable absorption pattern with decrease in the intensity of absorption from 5, 4, 3, 6 and 2, while the solid-state UV-visible absorption spectra of 2-6 are significantly different from the solution-state UV-visible absorption spectra. The considerable change in the fluorescent emission was observed upon complexation of 3 with corresponding metal precursors and the fluorescent emission was shifted towards the red region in the order of 2, 3, 6, 4 and 5 in water.