A. Pozzi

Characterization of ancient magnesian mortars coming from northern Italy

Abstract Different ancient mortar samples were analyzed to characterize their binder fraction. Thermal analyses (TG, DSC) proved to be very useful in the identification of three different species of lime composed of: (a) only calcite; (b) calcite and magnesite; (c) calcite, hydromagnesite and magnesite. The hydromagnesite is well identified in the DSC curve showing the peaks corresponding to the three-step thermal decomposition. Also the same mineral was detected by FTIR and/or micro-FTIR analyses, depending on its amount in the binder fraction of the mortar. Actually, the two absorption peaks characteristic of the hydromagnesite were often hidden by the wider peaks due to the asymmetric stretching of the carbonate ion, observed for the calcite and magnesite.

POlymeric Complexes of 3-Hydroxy-4-Methoxy- And 3-Methoxy-4-Hydroxybenzoic Acids. Crystal Structure of the Linear-Chain Complex of COII With 3-Hydroxy-4-Methoxybenzoic Acid

Abstract Reaction of CuII, CoII, and NiII with 3-hydroxy-4-methoxy- and 3-methoxy-4-hydroxybenzoic acids (hmba and mhba, respectively) yields hydrated complexes exhibiting stoicheiometries with 1:2 and 1:1 metal to ligand mol ratios. The 1:2 complexes, formed by CoII with hmba and CuII with mhba, involve carboxylate groups and water molecules as donors. The structure of [Co(hmba)2(H2O)3] was determined by single-crystal X-ray analysis. It crystallizes in the monoclinic space group 12/a with a = 8.164(2), b = 11.171(3), c = 20.980(5) A, β = 91.42(3)°, and Z = 4. The complex is a one-dimensional polymer with bridging water molecules (Co-H2O-Co = 128.04° and Co … Co = 4.082 A). The hexacoordination at each cobalt is completed by oxygens from two monodentate carboxylates and two water molecules. Stacking interactions between the parallel aromatic rings (3.5 A) hold neighbouring chains together. Complexes with a 1:1 metal to ligand ratio (M = CuII, CoII and NiII, L = hmba; M = CoII and NiII, L = mhba) also cle...

Flexibility in coordinative behavior of propane-1,3-diamine toward Zn(II) and Cd(II) halides:[M(1,3pn)2X2 (M=Zn, Cd; X=Cl, Br,I)].

Abstract A series of compounds of formula M(1,3pn)2X2 (M ue5fb Zn(II), Cd(II); 1,3pn=propane-1,3-diamine; X ue5fb Cl, Br, I) has been prepared; two of them (M ue5fb Zn, X ue5fb Cl) and (M ue5fb Cd, X ue5fb I) have been structurally characterized. The Zn(1,3pn)2Cl2 (I) compound crystallizes in the P21/c space group, with eight formula units in a cell of dimensions: a=12.833(4), b=16.753(9), c=13.010(4) A, β=118.88(3)°. The Cd(1,3pn)2I2 (II) compound crystallizes in the P21/n space group with four formula units in a cell of dimensions: a=12.406(3), b=8.655(2), c=14.372- (4) A, β=113.57(2)°. The structures were solved with the heavy-atom method and refined by full matrix least-squares to R and Rw values of 0.029 and 0.038, 0.042 and 0.058 for I and II respectively. The asymmetric unit of I consists of a dimeric [Zn- (1,3pn)2]24+ moiety, where both Zn ions are tetrahedrally coordinated to four nitrogen atoms belonging to one chelating and two bridging 1,3pn ligands. The dimeric moiety generates an infinite chain upon translation of one cell in the direction of the diagonal (1,0,1). The structure of II shows a polymeric arrangement of octahedral Cd atoms sharing both iodine atoms and 1,3pn ligands. The Mue5f8N stretching vibrations are discussed and assigned in the light of the known structures.

Syntheses and spectroscopic properties of halocadmates(II): crystal and molecular structure of a new tribromo[N-benzylpiperazinium]cadmium(II) compound

Abstract Compounds of formula [CdX4]·(LH2)·(H2O) (LH2 = N-benzylpiperazinium dication X = Cl, Br, I) and one of formula [CdBr3(LH)] (LH = N-benzylpiperazinium monocation) wem prepared and characterized. The crystal structure of the monoprotonated N-benzylpiperazinium tribromocadmate(II) complex was determined by means of X-ray analysis. The [CdBr3·(LH)] salt is triclinic (space group and lattice constants: P 1 , a = 9.500(3), b = 13.145(7), c = 6.801(1) A, α = 103.79(2), β = 96.24(2), γ = 96.17(5)°, Z = 2, R = 0.0392, Rw = 0.0394). Its structure consists of discrete monomeric [CdBr3(LH)] units, in which the coordination polyhedron around the cadmium ion is a distorted tetrahedron. The coordination sphere is comprised of the three anionic bromide ligands and one terminal N atom of the N-benzylpiperazinium monocation. All the compounds were also investigated by means of IR and Raman spectroscopic measurements. The Cdue5f8Br stretching vibrations of the structurally known [CdBr3·(LH)] salt were unambiguously assigned on the basis of calculations performed on its spectra and by comparison with literature data. The Cd-X stretching vibrations of the [CdX4]·(LH2)·(H2O) compounds, assigned by comparing their spectra with those of the monoprotonated N-benzylpiperazinium tribromocadmate and on the basis of literature data, strongly suggest the presence of discrete [CdX4]2− anions.

METAL COMPLEXES OF QUADRIDENTATE SCHIFF BASES WHICH CAN FORM A FOUR-MEMBERED CHELATE RING

Abstract The metal complexes of deprotonated N , N ′-bis(2-hydroxybenzylidene)arylmethanedimines show a strong preference for tetrahedral structures. Oxidation of the Co(II) derivatives gives compounds with S = 1.

Coordinative capabilities of substituted propane-1,3-diamine: Zinc(II) halide adducts of 2,2-dimethylpropane-1,3-diamine

Abstract A series of compounds of formula Zn(dmpd)nX2· mH2O (dmpd = 2,2-dimethylpropane-1,3-diamine, X = Cl, Br, I; n = 2, m = 0; n = 3, m = 1) has been prepared and studied by means of spectroscopic (IR and Raman) and structural investigations. The [Zn(dmpd)2]I2 (I) compound crystallizes in the tetragonal P42/nmc space group, with two formula units in a cell of dimensions: a = b = 8.417(2), c = 12.726(2) A. The structure consists of an ionic packing of iodide anions and of discrete [Zn(dmpd)2]2+ cations, where the Zn atoms are tetrahedrally coordinated to four nitrogen atoms of two chelating amine molecules. The [Zn(dmpd)3]Cl2·H2O (II) compound crystallizes in the triclinic space group P 1 , with Z = 2 and cell of dimensions: a = 9.021(2), b = 12.087(3), c = 13.785(3) A, α = 59.01(2), β = 70.35(2), γ = 76.01(2)°. The crystal consists of an ionic packing of discrete [Zn(dmpd)3]2+ cations and chloride anions plus two clathrate water molecules per unit cell. The Zn atom presents a trigonal bipyramidal geometry, being surrounded by four nitrogen atoms of two chelating dmpd molecules and one nitrogen of a monodentate dmpd ligand. The structures were solved by conventional Patterson and Fourier methods and refined by full matrix least-squares to R and Rw of 0.053 and 0.073, and 0.040 and 0.046 for I and II respectively. The Znue5f8N stretching vibrations are discussed and assigned in the light of the determined structures.

Coordinative capability of propane-l,3-diamine: spectroscopic and structural properties of a complex of formula [Cd(pnH)4CI2]Cl4

Abstract The compound [Cd(pnH)4Cl2]Cl4 (pn=propane-l,3-diamine) has been prepared and studied by means of spectroscopic (IR and Raman) and structural investigations. It crystallizes in the tetragonal P4nc space group (No. 104), with two formula units in a cell of dimensions: a=b=ll.972(4), c=9.129(4) A. The structure consists of an ionic packing of chlorine anions and of discrete [Cd(pnH)4Cl2]4+ cations; the Cd atoms are octahedrally coordinated to four nitrogen atoms of four distinct monoprotonated diamines and to two chlorine atoms in trans position to each other, showing very loose Cdue5f8Cl bonding interactions (2.680(3) and 2.884(2) A). The protonated ends of the propane-l,3-diamines interact with the non-coordinated chlorine ions via hydrogen bonding. The Cdue5f8N and Cdue5f8X stretching vibrations are discussed and assigned in the light of the known structures.

Cyanato copper(II) complexes with pyridine: Synthesis and characterization of two isomeric forms

Abstract A new solid isomeric form (α) of Cu(NCO) 2 py 2 was obtained as a first reaction product of copper nitrate, potassium cyanate and pyridine. This form can be transformed into the already known β form by recrystallization. Comparison of the spectroscopic and spectromagnetic properties of the two isomers suggests the absence of significant intermolecular interactions in the α form, the β one being characterized by a pseudo-bridging position of the NCO groups. The difference in the relative orientation of the tetragonal axes of the copper centers is responsible for different exchange coupling effects between the metal ions.