Synthesis and Characterization of Pyridine Functionalized Imidazolium Salt and its Silver(I) N-heterocyclic Carbene Complex

Reaction of imidazole with two equivalent of 2-picolyl chloride afforded bis (2-picolyl) imidazolium salts (1). Treatment of the synthesized imidazolium salt with silver(I) oxide resulted in the formation of bis NHC silver(I) complex (2). The compound was characterized spectroscopically (NMR, mass spectrometry), by elemental analysis and its molecular structure was analyzed using single crystal X-ray crystallographic analysis. The bis-N-heterocyclic carbene silver(I) complex synthesized shows approximately linear geometry around each of the silver atom of the type [Ag(NHC)2]+. The metal to ligand ratio was found to be 1:2.Keywords: Imidazolium salt, N-heterocyclic carbene, picolyl, silve

Synthesis, Characterization and Structure Report of Silver(I) N-heterocyclic Carbene Complex Derived from 1-Methyl-3-(4-picolyl) Imidazolium Salt

1-Methyl-3-(4-picolyl) imidazolium chloride was synthesized by the reaction of 4-picolyl chloride hydrochloride with 1-methyl imidazole. Treatment of the synthesized 1-methyl-3-(4-picolyl) imidazolium chloride with silver (I) oxide resulted in the formation of bis N-heterocyclic carbene (NHC) silver (I) complex. The compound was characterized spectroscopically using proton and carbon-13 nuclear magnetic resonance (NMR), and mass spectrometry. Its molecular structure was analyzed using single crystal X-ray crystallographic analysis. The bis-N-heterocyclic carbene silver(I) complex synthesized shows approximately linear geometry around each of the silver atom of the type [Ag(NHC)2]+.Keywords: N-heterocyclic Carbene, synthesis, characterization, X-ray crystallography, silver (I

Mild Regiospecific Synthesis of 1-Alkoxy-isochromenes Catalysed by Well-Defined [Silver(I)(Pc-L)] Complexes

The synthesis of 3-substituted-1-alkoxyisochromenes starting from 2-alkynylbenzaldehydes and different alcohols is reported. The reaction is catalysed by a silver(I)complex with an original macrocyclic pyridine-containing ligand (Pc-L). The approach is characterised by absolute regioselectivity, mild reaction conditions, good to excellent reaction yields, cleanness of the reaction and reduced purification steps. The reaction mechanism is investigated by in-depth 1H NMR experiments and an aimed \u201ctrapping\u201d experiment

Dual-Phosphorescent Heteroleptic Silver(I) Complex in Long-Lasting Red Light-Emitting Electrochemical Cells

The design of red-emitting silver(I) complexes and their implementation in thin-film lighting are still challenging as (i) their high ligand-field splitting energy leads to high-energy emissions with a controversial mechanism (thermally activated delayed fluorescence vs fluorescence/phosphorescence), and (ii) their low electrochemical stability leads to the formation of silver nanoclusters, limiting device stability to a few seconds. Herein, a thoughtful complex design [Ag(xantphos)(deebq)]PF6 combining a large-bite angle diphosphine ligand (xantphos), a rigid, sterically hindered, π-extended biquinolin (deebq) is reported. In contrast to prior-art, this complex possesses (i) efficient red-emission (λem = 660 nm; photoluminescence quantum yield of 42%) assigned to a thermally equilibrated dual-phosphorescent emission based on spectroscopic/theoretical studies and (ii) stable reduction behavior without forming silver nanoclusters. This results in the first red light-emitting electrochemical cells featuring (i) improved stability of two orders of magnitude compared to prior-art (from seconds to hours) at irradiances of 20 µW cm−2, and (ii) a new degradation mechanism exclusively related to p-doping as confirmed by electrochemical impedance spectroscopy analysis. Indeed, a multi-layered architecture to decouple hole injection/transport and exciton formation enables a further 2-fold enhanced irradiance/stability. Overall, this work illustrates that deciphering the rules for silver(I) complex design for lighting is tricky, but worthwhile.S.L. and L.M.C. contributed equally. R.D.C. acknowledges the European Union's Horizon 2020 research and innovation MSCA-ITN STiBNite No. 956923.Open access funding enabled and organized by Projekt DEAL.Peer reviewe

New Triazoloquinoxaline Ligand and its Polymeric 1D Silver(I) complex Synthesis, Structure, and Antimicrobial activity

The organic ligand 4-Benzyl-1-(N,N-dimethylamino)-[1,2,4]triazolo[4,3a]quinoxaline 1 (L) and its polymeric silver(I) complex, [Ag2L(NO3)2]n (2), have been synthesized and characterized. The organic ligand 1 crystallizes in the triclinic space group P¯1. The unit cell contains two parallel-stacked molecules. The complex [Ag2L(NO3)2]n (2) crystallizes in the monoclinic space group P21/n. The structure contains two different silver(I) ions. Ag(2) is coordinated by three oxygens (involving two nitrate groups) and to a nitrogen of the triazole ring of 1. These ligands form a strongly distorted tetrahedral, nearly planar coordination sphere. Ag(1) has an approximately tetrahedral geometry. It is bonded to one oxygen of a nitrate anion and a nitrogen of two different L; this aspect giving rise to an infinite chain structure. A final bond to Ag(1) involves the carbon of a phenyl group. It is more weakly bonded to the phenyl carbons on either side of this, so that the Ag(1)-phenyl bonding has aspects of an Ag-allyl bond. Ag(1) and Ag(2) participate in bonding to a common nitrate anion and alternate, the two distinct modes of bridging between them lead to a zig-zag chain structure. In addition to spectroscopic studies, the biological activities of the ligand and of the complex were scanned over a wide range of Gram positive and Gram negative flesh- and bone-eating bacteria. The results are discussed in comparison with well-known antibiotics

Poly[(μ4-5-bromo­pyridine-3-sulfonato)­silver(I)]

The silver(I) complex, [Ag(C5H3BrNO3S)]n, was obtained by reaction of AgNO3 and 5-bromopyridine-3-sulfonic acid. The AgI ion is coordinated by an O3N donor set in a slightly distorted tetra­hedral geometry. The AgI ions are linked by μ4-5-bromo­pyridine-3-sulfonate ligands, forming a layer parallel to (100). The layers are further connected via C—H⋯Br hydrogen-bonding inter­actions into a three-dimensional supra­molecular network. The Ag⋯Ag separation is 3.0159 (6) Å, indicating the presence of argentophilic inter­actions

Di-μ-bromido-tris­(triphenyl­phosphine)-1κP,2κ2 P-disilver(I) tetra­hydro­furan 0.85-solvate

In the title binuclear silver(I) complex, [Ag2Br2(C18H15P)3]·0.85C4H8O, the two independent silver(I) ions are briged by two bromide ions. One AgI ion is coordinated by two triphenyl­phosphine groups with a square-planar geometry, while the second is coordinated by one triphenyl­phine group with a trigonal-planar geometry. The structure is very similar to that of the dichloro­methane solvate reported by Zhu, Huang & Zheng [Chin. J. Struct. Chem. (1994), 13, 325–327]. The tetrahydrofuran solvent molecule is disordered and was refined with a fixed occupancy of 0.85

(4-Chloro­benzoato)bis(5-methyl-2-pyridylamine)silver(I)

The title compound, [Ag(C7H4ClO2)(C6H8N2)2], is a mononuclear silver(I) complex. The AgI atom is three-coordinated by two pyridine N atoms from two 5-methyl­pyridin-2-ylamine ligands and by one O atom of a 4-chloro­benzoate ligand, forming a distorted T-shaped coordination. In the crystal structure, the mol­ecules are linked through inter­molecular N—H⋯O hydrogen bonds, forming chains running along the b axis

Synthesis and antimicrobial evaluation of a pyrazoline-pyridine silver(I) complex: DNA-interaction and anti-biofilm activity

The emergence of resistant bacterial strains mainly due to misuse of antibiotics has seriously affected our ability to treat bacterial illness, and the development of new classes of potent antimicrobial agents is desperately needed. In this study, we report the efficient synthesis of a new pyrazoline-pyridine containing ligand L1 which acts as an NN-donor for the formation of a novel silver (I) complex 2. The free ligand did not show antibacterial activity. High potency was exhibited by the complex against three Gram-negative bacteria, namely Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumanii with the minimum inhibitory concentration (MIC) ranging between 4 and 16 μg/mL (4.2–16.7 μM), and excellent activity against the fungi Candida albicans and Cryptococcus neoformans (MIC ≤ 0.25 μg/mL = 0.26 μM). Moreover, no hemolytic activity within the tested concentration range was observed. In addition to the planktonic growth inhibition, the biofilm formation of both Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa was significantly reduced by the complex at MIC concentrations in a dose-dependent manner for Pseudomonas aeruginosa, whereas a biphasic response was obtained for MRSA showing that the sub-MIC doses enhanced biofilm formation before its reduction at higher concentration. Finally, complex 2 exhibited strong DNA binding with a large drop in DNA viscosity indicating the absence of classical intercalation and suggesting the participation of the silver ion in DNA binding which may be related to its antibacterial activity. Taken together, the current results reveal that the pyrazoline-pyridine silver complexes are of high interest as novel antibacterial agents, justifying further in vitro and in vivo investigation