Guillermo Díaz

Metal complexes of the antibiotic nalidixic acid

Abstract The preparations and spectral properties are reported of a range of complexes of nalidixic acid (= HNal) with some metal ions in the series CrZn and also Mg, Ca, Cd, Hg and Pd(II). Most of the compounds formed by the divalent metal ions had a 2:1 HNal:metal ratio, and some of them are polymeric. Complexes in which the carboxylate group of HNal functions as a chelate were isolated with Cu(II), Pd(II), Fe(III) and Cr(III).

Infrared spectrum of the bis-(1,10-phenanthroline) Cu(I) and Cu(II) perchlorate complexes

Abstract FT-IR spectra of the title compounds and derivatives were measured in the range 4000–120 cm −1 . A complete experimental spectral assignment has been performed. A simplified normal coordinate treatment orientates some assignment of frequencies in the low energy region. Bands at ca. 420 and 300 cm −1 are ascribed to the v Cu-N modes. A stability order of the Cu(I) complexes is proposed on the basis of their Cu-N frequency values.

Crystal structure and vibrational spectra of polyamine-copper(II) complexes

The structures of [Cu(en)(H2O)2]SO4 (I), [Cu(en)2](NO3)2 (II) and [Cu(trien)I]I (III) have been determined by single crystal X-ray diffraction. ComplexI is monoclinic, space group C2/c, with unit cell parametera=7.232(1),b=11.725(2),c=9.768(1), β=105.50(1)°, andZ=4. ComplexII is also monoclinic, space group P21/a, witha=7.978(2),b=9.982(4),c=8.218(3), β=111.11(2)°, andZ=2. ComplexIII is orthorhombic, space group P212121, witha=8.098(1),b=11.902(1),c=13.682(2), andZ=4. The structures were solved by direct methods and refined by full-matrix least-squares to finalR values of 0.031, 0.043 and 0.036 for complexesI, II, andIII, respectively. ComplexesI andII show an octahedral coordination geometry. ComplexIII shows a square pyramidal coordination geometry. ComplexI forms infinite monodimensional chains where the SO42− ions acts as a bridge between two neighboringen molecules. The vibrational spectra of these complexes agree well with their crystal structures. Structure and stability of seven other related Cu(II) complexes of (trien), (dien)2, (en)2 and (en) are inferred in this study.

Vibrational analysis and spectra of cytidine 3′-monophosphate (3′-CMP)

Abstract The FTIR and FT-Raman spectra of cytidylic acid b (cytidine 3′-monophosphate, 3′-CMP) and its hexadeuterated derivative (deuteration in the amino and hydroxyl groups) in the solid phase and aqueous solutions have been assigned on the basis of normal coordinate analysis. This was carried out using a valence force field based on force fields for simpler molecules and modified for 3′-CMP, as well as applying the semiempirical PM3 method. Assignments are discussed in the light of observed and calculated wavenumbers and isotopic shifts. The wavenumbers calculated with a large set of force constants result in lower deviation than the wavenumbers calculated by the PM3 method. The results obtained indicate vibrational coupling between the cytosine and ribose moieties of the nucleotide for some frequencies below 1400 cm −1 .

An improved synthetic method and vibrational study of (pentamethylcyclopentadienyl) dicarbonylrhenium dihalides (η5-C5Me5)Re(CO)2X2 (X = C1, Br and I)

An improved synthetic method has been found for the preparation of the pentamethylcyclopentadienyl rhenium dicarbonyldihalide complexes. From the reaction of (η5-C5Me5)Re(CO)3 with Br2 or I2 in THF-H2O a mixture of cis and trans isomers of (η5-C5Me5)Re(CO)2X2 X = Br and I is formed. On the other hand, the reaction of [(η5-C5Me5)Re(CO)3C1][SbC16] in water gives the cis-(η5-C5Me5)Re(CO)2C12 complex. The solid IR spectra of the dicarbonyldihalide complexes are recorded and an assignment of the normal modes in terms of local symmetry is suggested by comparison with those observed in analogous molecules. A normal coordinate analysis performed using a modified general valence force field and considering simplified models, confirms most of the experimental assignments. The set of valence force constants reflects the structure of the isomers under study.

Spectra and structure of polyamine-copper(II) complexes. Infrared spectrum and normal coordinate calculations of mono(diethylenetriamine) copper(II) nitrate

Abstract The infrared spectrum of mono(diethylenetriamine)copper(II) nitrate has been obtained in the frequency range 4000-80 cm −1 . Assignments of fundamental frequencies in the coordination site, as well as in the free and bonded nitrates, were performed regarding the structure of the complex. Also, a normal coordinate analysis based on a simplified model, was carried out in order to distinguish the frequency position of some normal modes, such as the three different ν(CuN) and the two different ν(CuO) modes.

Vibrational analysis of metal diimine dithiolate mixed ligand complexes

Abstract The IR spectra of the M(mnt)(baba) where M=Ni and Pd, mnt=1,2-maleonitrile and baba=biacetylbisanyline, were recorded in the high as well in the low energy region. A complete assignment of the observed bands was performed based on well-documented references. Further, a normal coordinate analysis was carried out taking into account C2v symmetry, and based in a simplified model in order to investigate the force field of both metal complexes and the potential energy distribution (PED) of the distinct modes of the quelate structure.

Vibrational study of polyamine copper(II) complexes. Infrared spectra and normal coordinate analysis of mono(diethylenetriamine)copper(II) complex ions

Abstract The results of an investigation of the infrared spectra of mono(diethylenetriamine)copper(II) compounds are reported, with particular reference to the low-energy region. Most assignments are based on the available literature. Assignments of the skeletal normal modes are supported by an approximate normal coordinate analysis, taking into account a modified general valence force field to obtain the frequencies and potential energy distribution.

N-(Substituted phenylhydroxynaphthylaldiminate) nickel(II) complexes: A structural and vibrational study

Abstract The crystal and molecular structure of bis-( N -phenyl-1-hydroxy-2-naphthylaldiminate) nickel(II) ( 1 ) have been determined by x-ray crystallography. The compound crystallizes in the triclinic space group P 1, No. 2 with one molecule in the unit cell. The metal adopts a trans -planar tetracoordination geometry with N and O as electron donor atoms. The molecule is stepped with the planes of two naphthyl groups parallel, each one making a dihedral angle of 20.4° with the coordination plane. The infrared spectrum and a normal coordinate treatment, based on a simplified molecular model, are discussed and related to the crystal structure. The bands near 390 and 290 cm −1 have been assigned to the Ni O and Ni N stretching vibrations, respectively. The corresponding force constants were estimated to be 1.28 and 0.78 mdyn A −1 . The influence of variation of the nature of the Schiff base ligand on structure 1 has been studied by including in the vibrational analysis the bis- N -(Y-phenyl)-2-hydroxy-1-naphthylaldiminate nickel(II) complexes, where substituents Y are o -OCH 3 ( 2 ), m -OCH 3 ( 3 ) and m -NO 2 ( 4 ). The results indicated a slightly lower electronic density distribution on the chelate ring in complex 1 , particularly on the Ni O bond, suggesting a stability order 1 ≈ 2 − 4 . This difference arises mainly from the position of the hydroxynaphthylaldiminate group.

The Infrared Spectra of Rhenium Pentamethyl Cyclopentadienyl Complexes: (n 5-C5Me5)Re(CO3) and [(n 5-C5Me5)Re(CO)3X]+ (X=Cl, Br, I)

Abstract The IR spectra of the title compounds are recorded and an assignment of the normal modes in terms of local symmetry is suggested by comparison with those observed in analogous molecules. A set of force constants calculated for simplified models confirms most of the experimental assignments and reflects the symmetry of the complexes under study. The f CO of the two different CO groups in the cationic complexes indicated that CO groups cis to the halide ligand should be more selective towards nucleophiles.