Synthesis and Structural Characterization of a Silver(I) Pyrazolato Coordination Polymer.

Coinage metal(I)···metal(I) interactions are widely of interest in fields such as supramolecular assembly and unique luminescent properties, etc. Only two types of polynuclear silver(I) pyrazolato complexes have been reported, however, and no detailed spectroscopic characterizations have been reported. An unexpected synthetic method yielded a polynuclear silver(I) complex [Ag(µ-L1Clpz)]n (L1Clpz- = 4-chloride-3,5-diisopropyl-1-pyrazolate anion) by the reaction of {[Ag(µ-L1Clpz)]3}2 with (nBu4N)[Ag(CN)2]. The obtained structure was compared with the known hexanuclear silver(I) complex {[Ag(µ-L1Clpz)]3}2. The Ag···Ag distances in [Ag(µ-L1Clpz)]n are slightly shorter than twice Bondi's van der Waals radius, indicating some Ag···Ag argentophilic interactions. Two Ag-N distances in [Ag(µ-L1Clpz)]n were found: 2.0760(13) and 2.0716(13) Å, and their N-Ag-N bond angles of 180.00(7)° and 179.83(5)° indicate that each silver(I) ion is coordinated by two pyrazolyl nitrogen atoms with an almost linear coordination. Every five pyrazoles point in the same direction to form a 1-D zig-zag structure. Some spectroscopic properties of [Ag(µ-L1Clpz)]n in the solid-state are different from those of {[Ag(µ-L1Clpz)]3}2 (especially in the absorption and emission spectra), presumably attributable to this zig-zag structure having longer but differently arranged intramolecular Ag···Ag interactions of 3.39171(17) Å. This result clearly demonstrates the different physicochemical properties in the solid-state between 1-D coordination polymer and metalacyclic trinuclear (hexanuclear) or tetranuclear silver(I) pyrazolate complexes.

Structure and photoluminescence of silver(i) trinuclear halopyrazolato complexes.

Five halogen substituted pyrazolates, 4-chloro-3,5-diisopropylpyrazole (4-Cl-3,5-iPr2pzH), 4-bromo-3,5-diisopropylpyrazole (4-Br-3,5-iPr2pzH), 4-iodo-3,5-diisopropylpyrazole (4-I-3,5-iPr2pzH), 4-chloro-3,5-diphenylpyrazole (4-Cl-3,5-Ph2pzH), and 4-bromo-3,5-diphenylpyrazole (4-Br-3,5-Ph2pzH), were conveniently prepared by halogenation of the appropriate pyrazoles with N-halosuccinimides (NXS) (X = Cl, Br, and I) followed by complexation of the pyrazolate anions with silver(i) nitrate. Single crystal X-ray analysis revealed either dimeric trinuclear {[Ag(µ-4-X-3,5-R2pz)]3}2 (R = iPr, X = Cl, Br, and I) or trinuclear [Ag(µ-4-X 3,5-R2pz)]3 (R = iPr, X = I; R = Ph, X = Cl, R = Ph, X = Br) structures, the latter held together with argentophilic interactions (AgAg interactions) that could also be observed in the Raman spectra. The electronegativity of the halogen substituent could be correlated with the strength of the AgAg interaction and the wavelength of solid-state photoluminescence. All complexes were emissive on UV irradiation at low temperatures, with the colour of emission from the diisopropyl substituted analogues red shifted by the halogens in the order Cl (red) > Br (orange) > I (yellow). Emission from the diphenyl substituted analogues was dominated by the extended aromatic system and was largely invariant to the halogens.

Conversion of carbon dioxide to oxalate by α-ketocarboxylatocopper(II) complexes.

The α-ketocarboxylatocopper(II) complex [{Cu(L1)}{O2CC(O)CH(CH3)2}] can be spontaneously converted into the binuclear oxalatocopper(II) complex [{Cu(L1)}2(µ-C2O4)] upon exposure to O2/CO2 gas. (13)C-labeling experiments revealed that oxalate ions partially incorporated (13)CO2 molecules. Furthermore, the bicarbonatocopper(I) complex (NEt4)[Cu(L1){O2C(OH)}] in an Ar atmosphere and the α-ketocarboxylatocopper(I) complex Na[Cu(L1){O2CC(O)CH(CH3)2}] in an O2 atmosphere were also transformed spontaneously into the oxalato complex [{Cu(L1)}2(µ-C2O4)].