Dicyanamide mediated construction of 1D polymeric networks of quinoxaline with d10 metal ions: Synthesis, thermogravimetric analysis, photoluminescence and a theoretical investigation on the π⋯π interactions

Synthesis, Structure and Reactivity of a Cyapho-Cyanamide Salt

We describe a facile synthesis of the cyapho-cyanamide salt [Na(18-crown-6)][N(CN)(CP)] from reaction of [Na(18-crown-6)][PH₂ ] (18-crown-6=1,4,7,10,13,16-hexaoxacyclooctadecane) with dimethyl N-cyanocarbonimidate, (MeO)₂ C=N(CN). The reaction proceeds with elimination of two equivalents of methanol. Careful tuning of the reaction conditions allowed for the isolation and characterization of the N-cyano(carboximidate)phosphide intermediate [HP{C(OMe)N(CN)}]^- . Due to the adverse effects of methanol in these reaction mixtures, a bulk scale synthesis of [Na(18-crown-6)][N(CN)(CP)] could be achieved by addition of a base (LiHMDS) to neutralize the resulting alcohol. Further reactivity studies of this anion reveal that functionalization at the phosphorus atom is viable to yield a new family of cyanide-functionalised phosphorus heterocycles.

Coordination Polymers in Dicyanamido-Cadmium(II) with Diverse Network Dimensionalities

The synthesis and structural characterization of six dicyanamido-cadmium(II) complexes are reported: catena-[Cd(μ1,3-dca)(μ1,5-dca)(3-ampy)] (1), catena-[Cd3(μ1,3,5-dca)2(μ1,5-dca)4(pyNO)2(H2O)2] (2), catena-{Cd(H2O)2(μ1,5-dca)2](2,6-lut-NO)} (3), catena-[Cd(Me2en)(μ1,5-dca)2] (4), catena-[Cd(Me4en)(μ1,5-dca)2] (5), and [Cd(1,8-damnp)2(dca)2] (6), where dca = dicyanamide anion, 3-ampy = 3-aminopyridine, pyNO = pyridine-N-oxide, 2,6-lut-NO = 2,6-lutidine-N-oxide, Me2en = N,N-dimethyl-ethylenediamine, Me4en = N,N,N′,N′-tetramethyl-ethylenediamine, and 1,8-damnp = 1,8-diaminonaphthaline. The coordination polymers have different dimensionalities: 1 and 5 form 3D networks structures; 3 and 4 form polymeric 1D chains and 1DD double chains, respectively. Ribbons of three fused polymeric chains are observed in 2. In 6, the mononuclear complex units form a hydrogen-bonded supramolecular 3D network. In the coordination polymer compounds, the dca linkers display three bonding modes: the most common μ1,5-dca and the least popular μ1,3- and μ1,3,5-dca bonding. The luminescence emission and thermal properties of the complexes were investigated.

Structure, DFT Calculations, and Magnetic Characterization of Coordination Polymers of Bridged Dicyanamido-Metal(II) Complexes

Three coordination polymers of metal(II)-dicyanamido (dca) complexes with 4-methoxypyridine-N-oxide (4-MOP-NO); namely, catena-[Co(µ1,5-dca)2(4-MOP-NO)2] (1), catena-[Mn(µ1,5-dca)2(4-MOP-NO)2] (2), catena-[Cd(µ1,5-dca)2(4-MOP-NO)2] (3), and the mononuclear [Cu(κ1dca)2(4-MOP-NO)2] (4), were synthesized in this research. The complexes were analyzed by single crystal X-ray diffraction as well as spectroscopic methods (UV/vis, IR). The polymeric 1-D chains in complexes 1–3 were achieved by the doubly µ1,5-bridging dca ligands and the O-donor atoms of two axial 4-MOP-NO molecules in trans configuration around the distorted M(II) octahedral. On the other hand, the two “trans-axial” pyridine-N-oxide molecules in complexes 2 and 3 display opposite orientation (s-trans). The DFT (density functional theory) computational studies on the complexes 1–3 were consistent with the experimentally observed crystal structures. Compounds 1 and 2 display weak antiferromagnetic coupling between metal ions (J = −10.8 for 1 and −0.35 for 2).

Synthesis of Heavy Dicyanamide Homologues from Air-Stable Precursors

A convenient synthesis of dicyanophosphide and dicyanoarsenide anions is reported. These heavy homologues of the long-known and fundamentally important dicyanamide anion were formed through the nucleophilic displacement of bis(diphenylphosphino)ethane (dppe) from the pnictogen⁺ transfer agents [dppePn][BPh₄ ] (Pn=P, As) by exposure to cyanide salts. The protocol requires three synthetic steps from commercially available materials and the [dppePn][BPh₄ ] salts are remarkably temperature, air, and moisture stable. All products have been fully characterized by spectroscopic methods and by single-crystal X-ray diffraction, and the electronic structures of the DCPn anions have been assessed computationally.

Architectures varying from discrete molecular units to 2-dimensional coordination polymers and photoluminescence behavior of zinc and cadmium comprising an anionic zwitterion of rigid 4,5-dicarboxy-1,3-dimethyl-1H-imidazolium iodide

A rigid ligand, 4,5-dicarboxy-1,3-dimethyl-1H-imidazolium iodide (H₂DDII) and crystallized as zwitterion (1) and employed in the synthesis of anionic zwitterion complexes or coordination polymers (CPs)2–6of Zn(ii) and Cd(ii).