Dicyanamide Research Articles

Two Photoluminescent Metal–Organic Frameworks Constructed from Cd3(μ3‐OH) Cluster or 1D Zn5(μ3‐OH)2(μ‐OH)2 Chain Units and In Situ Formed Bis(tetrazole)amine Ligands

AbstractHydrothermal reactions of CdCl2·2.5H2O or ZnCl2, sodium dicyanamide, and sodium azide yield two interesting photoluminescent coordination polymers, namely, [Cd{Cd3(μ3‐OH)(dcadtzH)3(H2O)6}2] (1) and [Zn5(μ3‐OH)2(μ‐OH)2(dcadtz)2]·2H2O (2) [dcadtzH3 = bis(5‐tetrazolyl)amine], in which triangular [Cd3(μ3‐OH)]5+ cluster subunits in 1 and 1D [Zn5(μ3‐OH)2(μ‐OH)2]n6n+ chain subunits in 2 are linked by in situ generated bis(tetrazole)amine ligands to generate an interesting 2D coordination net and a 3D microporous metal–organic framework, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Dicyanamide anion based ionic liquids for electrodeposition of metals

Electrodeposition of Al, Mn, Ni, Zn, Sn, and Cu are successfully demonstrnated in the ionic liquids (ILs) composed of 1-methyl-3-alkylimidazolium or N-methyl- N-alkylpyrrolidinium cations with dicyanamide (DCA) anions. The DCA-based room-temperature ILs exhibit lower viscosities than those ILs based on BF 4 - , PF 6 - , and bis(trifluoromethylsulfonyl)imide (TFSI) anions. While most of the metal chlorides are insoluble in the BF 4 - , PF 6 - , and TFSI-based ILs, they exhibit good solubility in DCA-based ILs due to the strong complexing ability of DCA toward the transition metal ions. It is possible to alter the regular reduction sequence for particular metal ions in the DCA-based ILs.

Reorientational Dynamics and Solid-Phase Transformation of Ammonium Dicyanamide into Dicyandiamide

The reorientational dynamics of ammonium dicyanamide ND4[N(C≡N)2] and the kinetics as well as the mechanism of the solid-state isomerization reaction from ammonium dicyanamide into dicyandiamide (N≡C-N=C(NH2)2) was studied by means of 2H and 14N solid-state NMR spectroscopy in a temperature range between 38 and 390 K. Whereas in previous investigations the mechanism of the solid-state transformation was investigated by means of vibrational and magic angle spinning solid-state NMR spectroscopy as well as neutron diffraction, we here present a comprehensive 2H study of the ammonium ion dynamics prior to and during the course of the reaction, thereby highlighting possible cross correlations between dynamics and reactivity involving the ammonium ion. The ND4+ group was found to undergo thermally activated random jumps in a tetrahedral potential, which is increasingly distorted with increasing temperature, giving rise to an asymmetrically compressed or elongated tetrahedron with deviations from the tetrahedral angle of up to 6°. The correlation time follows an Arrhenius law with an activation energy of Ea = 25.8(2) kJ mol-1 and an attempt frequency of τ0-1 = 440(80) THz. The spin−lattice relaxation times were fitted according to a simple Bloembergen−Purcell−Pound type model with a T1 minimum of 4 ms at 230 K. Temperature-dependent librational amplitudes were extracted by line-shape simulations between 38 and 390 K and contrasted with those obtained by neutron diffraction, their values ranging between 5 and 28°. The onset and progress of the solid-phase transformation were followed in situ at temperatures above 372 K and could be classified as a strongly temperature-dependent, heterogeneous two-step reaction proceeding with rapid evolution of ammonia and comparatively slow subsequent reintegration into the solid. On the microscopic level, this correlates with a rapid proton transferpossibly triggered by a coupling between the ammonium ion dynamics and phonon modes on the terahertz time scaleand an essentially decoupled nucleophilic attack of ammonia at the nitrile carbon, giving rise to significantly differing time constants for the two processes.

Trimerization of NaC2N3 to Na3C6N9 in the Solid

Sodium dicyanamide NaC2N3 was found to undergo two phase transitions. According to thermal analysis and temperature-dependent X-ray powder diffractometry, the transition of α-NaC2N3 (1a) to β-NaC2N3 (1b) occurs at 33°C and is displacive. 1a crystallizes in the monoclinic system, space group P21/n (no. 14), with a = 647.7(1), b = 1494.8(3), c = 357.25(7) pm, β = 93.496(1)°, and Z = 4. The structure was solved from powder diffraction data (Cu Kα1, T = 22°C) using direct methods and it was refined by the Rietveld method. The final agreement factors were wRp = 0.072, Rp = 0.053, and RF = 0.074. 1b crystallizes in the orthorhombic system, space group Pbnm (no. 62), with a = 650.15(5), b = 1495.1(2), c = 360.50(3) pm, and Z = 4. The structure was refined by the Rietveld method using the atomic coordinates of 1a as starting values (Mo Kα1, T = 150°C). The final agreement factors were wRp = 0.044, Rp = 0.034, RF = 0.140. The crystal structures of both polymorphs contain sheets of Na+ and N(CN)2- ions which are in 1a nearly and in 1b exactly coplanar. Above 340°C, 1b trimerizes in the solid to Na3C6N9 (2). 2 crystallizes in the monoclinic system, space group P21/n (no. 14), with a = 1104.82(1), b = 2338.06(3), c = 351.616(3) pm, β = 97.9132(9)°, and Z = 4. The structure was solved from synchrotron powder diffraction data (λ = 59.733 pm) using direct methods and it was refined by the Rietveld method. The final agreement factors were wRp = 0.080, Rp = 0.059, and RF = 0.080. The compound contains Na+ and the planar tricyanomelaminate C6N93-. The phase transition from 1b to 2 is reconstructive. It occurs in the solid-state without involvement of other phases or intermediates. The crystal structures of 1b and 2 indicate that there is no preorientation of the N(CN)2- in the solid before their trimerization to C6N93-.