Characterization and crystal structure of cadmium(II) halide complexes with amino acids and their derivatives: VII. Crystal structures of aquadibromo(3-aminopropanoic acid)cadmium(II), dichloro(4-aminobutanoic acid)cadmium(II), diaquabis(aminohexanoic acid)cadmium(II) tetrachlorocadmium(II), and dibromo(azetidine-3-carboxylic acid)cadmium(II).

Seven cadmium complexes: [CdX2(Hapro)(H2O)n] (X: Cl(1), Br(2)), [CdX2(Hgaba)] (X: Cl(3), Br(4)), [Cd(Hahex)2(H2O)2][CdCl4] (5), and [CdX2(Haze-3)](H2O)n (X: Cl(6), Br(7)) have been prepared and investigated by means of IR and FT Raman spectra. The crystal and molecular structures of 2, 3, 5 and 7 were determined by a single-crystal X-ray diffraction method. In complex 2, the cadmium atom is in a distorted octahedral geometry, ligated by two carboxyl oxygen atoms of Hapro, a water molecule, and three bromine atoms; one is terminal and each of the other two is bridging two cadmium atoms to make a polymer. The structure of 3 consists of one-dimensional polymers bridged by two chlorine atoms and a carboxyl group. The carboxyl oxygen atoms of Hgaba coordinate forkedly to two cadmium atoms. The cadmium atom of [Cd(Hahex)2(H2O)2]2+ in complex 5 is in a distorted octahedral geometry, ligated by four carboxyl oxygen atoms of two molecules of Hahex and by two water molecules. [Cd(Hahex)2(H2O)2]2+ exists between two layers which are formed of infinite [CdCl4]2- chains. The carboxyl oxygen atoms of Hahex coordinate to the same cadmium atom. In complex 7, the cadmium atom is ligated by two carboxyl oxygen atoms and four bridging bromine atoms to make a polymer.

Spontaneous resolution of binary copper(II) complexes with racemic dipeptides: crystal structures of glycyl-L-alpha-amino-n-butyrato copper(II) monohydrate, glycyl-D-valinato copper(II) hemihydrate, and glycyl-L-valinato copper(II) hemihydrate.

Copper(II) complexes with glycyl-DL-alpha-amino-n-butyric acid (H2gly-DL-but), glycyl-DL-valine (H2gly-DL-val), glycyl-DL-norleucine (H2gly-DL-norleu), glycyl-DL-threonine (H2gly-DL-thr), glycyl-DL-serine (H2gly-DL-ser), glycyl-DL-phenylalanine (H2gly-DL-phe), and glycyl-L-valine (H2gly-L-val), have been prepared and characterized by IR, powder diffuse reflection, CD and ORD spectra, and magnetic susceptibility measurements, and by single-crystal X-ray diffraction. The crystal structures of the copper complex with H2gly-DL-but, the copper complex with H2gly-DL-val, and [Cu(gly-L-val)]n.0.5nH2O have been determined by a single-crystal X-ray diffraction method. As for the structure of the copper complex with H2gly-DL-but, the configuration around the asymmetric carbon atom is similar to that of [Cu(gly-L-val)]n.0.5nH2O. Therefore it is concluded that the copper complex with H2gly-DL-but is [Cu(gly-L-but)]n.nH2O. On the contrary, as for the structure of the copper complex with H2gly-DL-val, the configuration around the asymmetric carbon atom is different from that of [Cu(gly-L-val)]n.0.5nH2O. Therefore it is concluded that the copper complex with H2gly-dl-val is [Cu(gly-D-val)]n.0.5nH2O. So during the crystallization of the copper(II) complexes with H2gly-DL-but and H2gly-DL-val, spontaneous resolution has been observed; the four complexes have separated as [Cu(gly-D-but)]n.nH2O, [Cu(gly-L-but)]n.nH2O, [Cu(gly-D-val)]n.0.5nH2O, and [Cu(gly-L-val)]n.0.5nH2O, respectively. [Cu(gly-L-but)]n.nH2O is orthorhombic with the space group P2(1)2(1)2(1). [Cu(gly-D-val)]n.0.5nH2O and [Cu(gly-L-val)]n.0.5nH2O are monoclinic with the space group C2. In these complexes, the copper atom is in a square-pyramidal geometry, ligated by a peptide nitrogen atom, an amino nitrogen atom, a carboxyl oxygen atom, and a carboxyl oxygen atom and a peptide oxygen atom from neighboring molecules. So these complexes consist of a two-dimensional polymer chain bridged by a carboxyl oxygen atom and a peptide oxygen atom from neighboring molecules. The axial oxygen atom is located above the basal plane and the side chain of an amino acid is located below it. These polymer chains consist of only one or the other type of optical isomers; no racemic dipeptides are found. Therefore, spontaneous resolution has been observed in the crystallization of copper(II) complexes with H2gly-DL-but and H2gly-DL-val. The crystal structure of [Cu(gly-D-val)]n.0.5nH2O agrees almost completely with that of [Cu(gly-L-val)]n.0.5nH2O, except for the configuration around the asymmetric carbon atom.

Characterization and crystal structure of cadmium(II) halide complexes with amino acids and their derivatives VI. The comparison of crystal structures of cadmium(II) halide complexes with three kinds of piperidine carboxylic acids.

Six cadmium(II) halide complexes with dl-piperidine-2-carboxylic acid (DL-Hpipe-2), dl-piperidine-3-carboxylic acid (DL-Hpipe-3), and piperidine-4-carboxylic acid (Hpipe-4), have been prepared and characterized by means of IR and Raman spectra and thermal analysis. The crystal structures of [CdCl2(DL-Hpipe-2)(H2O)], [CdBr2(DL-Hpipe-3)], and [CdCl2(Hpipe-4)] have been determined by X-ray diffraction. These three complexes have one-dimensional polymer structures bridged by halide atoms. The crystal of [CdCl2(DL-Hpipe-2)(H2O)] is orthorhombic with the space group Pca2(1). The cadmium atom is in an octahedral geometry, ligated by a carboxyl oxygen atom, two bridging chlorine atoms, a terminal chlorine atom, a water molecule and a carboxyl oxygen atom of a neighboring molecule. The carboxyl oxygen atoms of DL-Hpipe-2 are coordinated to two cadmium atoms. The unit cell consists of two types of one-dimensional polymer structures: [CdCl2(D-Hpipe-2)(H2O)] and [CdCl2(L-Hpipe-2)(H2O)]. Therefore, it is better to write [CdCl2(DL-Hpipe-2)(H2O)] as [CdCl2(D-Hpipe-2)(H2O)][CdCl2(L-Hpipe-2)(H2O)]. The crystal structure of [CdBr2(DL-Hpipe-3)] is monoclinic with space group P2(1). The cadmium atom is in a distorted octahedral geometry ligated by two carboxyl oxygen atoms and four bridging bromine atoms. This complex consists of either D-Hpipe-3 or L-Hpipe-3. Therefore [CdBr2(DL-Hpipe-3)] is written as [CdBr2(D or L-Hpipe-3)]. The crystal of [CdCl2(Hpipe-4)] is monoclinic with space group P2(1)/n. The structure is similar to that of [CdBr2(D or L-Hpipe-3)].