1. A cobalt(III) compound of a 13-membered cyclic tetraamine: trans-(12,12-dimethyl-1,4,7,10-tetraazacyclotetradecane)diisothiocyanatocobalt(III) tetraisothiocyanatozinc(II) ethanol solvate
Neil F Curtis, Kelly Flood, Ward T Robinson Acta Crystallogr C. 2006 Feb;62(Pt 2):m78-80. doi: 10.1107/S0108270105042940. Epub 2006 Jan 31.
The title compound, [Co(NCS)2(C11H26N4)]2[Zn(NCS)4].C2H5OH, has two similar cations with the Co(III) atom coordinated in a planar fashion by the 13-membered cyclic tetraamine, in the 1R,4S,7R,10S configuration, and with trans isothiocyanate ligands. The six-membered chelate ring is in a chair conformation, with one axially and one equatorially oriented methyl substituent [mean Co-N = 1.948 (2) A]. The ;opposite' chelate ring (N4 and N7) is in an eclipsed conformation [mean Co-N = 1.928 (2) A], and the ;side' chelate rings have gauche conformations. The mean Co-N(NCS) distance is 1.928 (2) A. Both cations have one Co-N-C group nearly linear and the other appreciably bent, with mean Co-N-C angles of 178.7 (1) and 160.4 (1) degrees , respectively. The [Zn(NCS)4]2- anion is approximately tetrahedral, with Zn-N = 1.951 (1)-1.986 (1) A, N-Zn-N = 104.5 (1)-111.9 (1) degrees and Zn-N-C = 152.5 (1)-179.4 (1) degrees. One NH group is hydrogen bonded to the ethanol O atom and the other NH groups are bonded to thiocyanate S atoms, forming a network.
2. The interplay of solvation, molecular conformation and supramolecular assembly in 1,1'-({[(ethane-1,2-diyl)dioxy](1,2-phenylene)}bis(methanylylidene))bis(thiosemicarbazide) and its N,N-dimethylformamide disolvate
Shaaban K Mohamed, Sabry H H Younes, Eman M M Abdel-Raheem, Joel T Mague, Mehmet Akkurt, Christopher Glidewell Acta Crystallogr C Struct Chem. 2015 Nov;71(Pt 11):959-64. doi: 10.1107/S2053229615018744. Epub 2015 Oct 13.
The wide diversity of applications of thiosemicarbazones and bis(thiosemicarbazones) has seen them used as anticancer and antitubercular agents, and as ligands in metal complexes designed to act as site-specific radiopharmaceuticals. Molecules of 1,1'-({[(ethane-1,2-diyl)dioxy](1,2-phenylene)}bis(methanylylidene))bis(thiosemicarbazide) {alternative name: 2,2'-[ethane-1,2-diylbis(oxy)]dibenzaldehyde bis(thiosemicarbazide)}, C18H20N6O2S2, (I), lie across twofold rotation axes in the space group C2/c, with an O-C-C-O torsion angle of -59.62 (13)° and a trans-planar arrangement of the thiosemicarbazide fragments relative to the adjacent aryl rings. The molecules of (I) are linked by N-H...S hydrogen bonds to form sheets containing R(2)4(38) rings and two types of R(2)2(8) ring. In the N,N-dimethylformamide disolvate, C18H20N6O2S2·2C3H7NO, (II), the independent molecular components all lie in general positions, but one of the solvent molecules is disordered over two sets of atomic sites having occupancies of 0.839 (3) and 0.161 (3). The O-C-C-O torsion angle in the ArOCH2CH2OAr component is -75.91 (14)° and the independent thiosemicarbazide fragments both adopt a cis-planar arrangement relative to the adjacent aryl rings. The ArOCH2CH2OAr components in (II) are linked by N-H...S hydrogen bonds to form deeply puckered sheets containing R(2)2(8), R(2)4(8) and two types of R(2)2(38) rings, and which contain cavities which accommodate all of the solvent molecules in the interior of the sheets. Comparisons are made with some related compounds.
3. Preparation and structural characterization of cDHAP-cyclic form of dihydroxyacetone phosphate-revealing chair and skew conformations of 1,3,2-dioxaphosphorinane ring
Katarzyna Slepokura Carbohydr Res. 2013 Mar 7;368:96-103. doi: 10.1016/j.carres.2012.12.020. Epub 2012 Dec 28.
A cyclic form of dihydroxyacetone phosphate, cDHAP, was obtained by the acidic hydrolysis of its dimethyl acetal (MeO)(2)cDHAP, and was crystallized in the hydrate, cDHAP-H (gem-diol; 1,3,2-dioxaphosphinane-2,5,5-triol 2-oxide) and the ketone, cDHAP-K (2-hydroxy-1,3,2-dioxaphosphinan-5-one 2-oxide) forms. The synthesis, MS and NMR analyses, crystallization and solid state structures determined by X-ray crystallography are described. The equilibrium state between the hydrate and ketone was established, revealing ~86% of cDHAP-H in aqueous solution at room temperature. The striking structural feature of the ketone and hydrate forms of the same cyclic phosphate diester in the crystalline state is different conformations of the six-membered P/O/C/C/C/O 1,3,2-dioxaphosphorinane ring, namely chair (C) in cDHAP-H·H2O (9a-H) and skew (S) in cDHAP-K (9a-K). Apart from one previous report on the non-chair-puckered, disordered [(MeO)2cDHAP]- anion in the crystal of its ammonium salt (Ślepokura, K. Carbohydr. Res. 2008, 343, 113-131), this is the unique example of the cyclic phosphate diester in skew conformation. Both 9a-H and 9a-K crystallize with the phosphate group protonated, which has been so far rarely observed in the cyclic phosphates. Deformation of the phosphate group and flattening of the chair-puckered ring in 9a-H is typical of protonated P/O/C/C/C/O rings. However, the skew-puckered 9a-K shows different values of O-P-O angles versus the same lengths of P-O(endo) and P-O(exo) bonds.
