One-Dimensional Cadmium Polymers with Alternative di(EO/EE) and di(EO/EO/EO/EE) Bridged Azide Bonding Modes

Abstract

Four new doubly bridged Cd(II)-azido complexes derived from sterically hindered NNN- and NN-donors were synthesized and structurally characterized. The tridentate amine ligands 2-methylquinolyl-2(ethyl-2-pyridyl)-methylamine (Meepmqa) and bis(2-methylypyridyl)methylamine (MeDPA) afforded the dinuclear complexes [Cd2(Meepmqa)2(μ1,3-N3)2(N3)2] (1) and [Cd2(MeDPA)2(μ1,1-N3)2(N3)2] (2) with di-EE- and di-EO-azido bridges, respectively. The N-substituted trialkyl ethylenediamine compounds N,N,N′-triethylethylenediamine (Et3en) and N,N,N′-trimethylethylenediamine (Me3en) resulted in the formation of 1D-polymeric chains {[Cd2(Et3en)2(μ1,1-N3)2(μ1,3-N3)2]} n (3) and {[Cd4(Me3en)4(μ1,1-N3)6(μ1,3-N3)2]} n (4) with alternative (di-EO/di-EE)- and di(EO/EO/EO/EE)-azido bonding modes. The IR asymmetric stretching vibration, νas(N3) of the azido ligands in these complexes and in related complexes, were analyzed in an attempt to predict the coordination bonding mode of the bridged azide. The fluorescence properties of the ligand Meepmqa and its complex 1 are reported. The Cd-complex 1 has increased fluorescence intensity compared to its free ligand. This was attributed to the strong Cd–N bond of the quinolyl group of Meepmqa and the nonflexibility of the corresponding five-membered chelate ring.

Investigation of the crystal structure and electrochemical properties of catena-poly[[chlorido(piperazin-1-ium–κN))cadmium(II)]-di-μ-chlorido]monohydrate

“…According to previous reports, the luminescence behavior of the complex may be attributed to the intraligand transition, because the free piperazine ligand has an emission band at 418 nm on excitation at 312 nm [32]. The red shift and the greater intensity are, presumably, because of the increase in conformational rigidity of the ligand on coordination [30,33,34].…”

Pyridyl and triazole ligands directing the assembling of zinc(II) into coordination polymers with different dimensionality through azides

“…The design of these compounds necessitates the incorporation of bridging ligands into the reaction mixtures. The most common bridging ligands which have been used for this purpose include aromatic and heterocyclic polycarboxylates, [1,2] benzenoid aromatic oxocarbon dianions, C n O n 2− (n = 4, squarate; n = 5, croconate) [3] and small pseudohalides (azide, N 3 -; thiocyanate, NCS -; cyanate, OCN -) [4][5][6][7][8][9] as well as the larger molecular dicynamide ion, NCNCN -(dca) [10]. These ligands have the capability to simultaneously bind several metal ions and hence act as bridging linkers to assemble metal ions in different nuclearity and in 1-, 2-, or 3D extended polymeric networks resulted in the isolation of many coordination compounds with interesting molecular and crystalline architectures.…”

“…[4(c), 5,7] Now, it is known that d 10 metal ions and in particular Zn(II) and Cd(II) ions in certain complexes or metal-organic frameworks (MOFs) can enhance or quench the fluorescence emission of their parent organic ligand from which complexes were derived. [7,[33][34][35] The photoinduced electron transfer (PET) process in these complexes results from the excitation of the lone-pairs of electrons which are located in the donor atoms of the ligand. Upon complexation and/or chelation of the organic ligand with metal ion, the PET process may be suppressed or prevented and as a result the fluorescence intensity may be enhanced.…”

“…Upon complexation and/or chelation of the organic ligand with metal ion, the PET process may be suppressed or prevented and as a result the fluorescence intensity may be enhanced. [7,[34][35][36] In a continuous effort to explore the chemistry of azido compounds and the luminescence properties of d 10 metal ions, [7,35] a new series of Zn(II)-azido complexes were synthesized based on pyridyl {3-aminopyridine (3-ampy), 5-ethyl-2-methylpyridine (5-Et-2-Mepy), 4-hydroxypyridine (4-HOpy), 2-hydroxypyridine-N-oxide (2-HO-py-N-oxide)} and 4-amino-4H-1,2,4-triazole (4-amtz)…”

Zinc(II) and Cadmium(II) complexes with N4-coordinate pyrazole based ligand: Syntheses, characterization and structure

“…Transition metal complexes containing bridging ligands like azide, thiocyanate and isocyanate are very interesting because of their various modes of coordination and formation of mono, di-and polynuclear complexes [1][2][3][4][5][6][7]. Among these bridging ligands, azide and thiocyanate anion are versatile ligands.…”