Wyniki wyszukiwania - BazTech

1

Synthesis and Spectroscopic Studies of the Nicotinamide Adducts of Cobalt(II), Nickel(II) and Zinc(II) Chlorides

Çakir S., Biçer E., Içbudak H., Naumov P., Korkmaz H., Çakir O.

Polish Journal of Chemistry

|

2001

|

Vol. 75, nr 3

371-377

EN

Nicotinamide (na) adducts of Co(II), Ni(II) and Zn(II) chlorides are synthesized and characterized by thermoanalytical methods (TG, DTG, DTA), FT IR (4000-400 cm-1) and UV/Vis spectroscopy. Structural similarity is inferred between the octahedral Co and Ni compounds of type [M(na)2(H2O)4]Cl2. The tetrahedral Zn complex [Zn(na)2Cl2] presents a different structure. The coordination of the metal ions in the Co and Ni adducts modelled by semiempirical theoretical methods compares well with the structural data for [Ni(na)2(H2O)4](NO3)2_2H2O.

2

Semiempirical Calculations in a Search for a Mechanism of 2-Methyl-4-phenylquinoline Formation from 4,4-Diphenyl-3-buten-2-one Oxime Acetate

Suwiński J., Mohamed M. A. A.

Polish Journal of Chemistry

|

2001

|

Vol. 75, nr 7

965-974

EN

The known thermal non-catalytic formation of 2-methyl-4-phenylquinoline from 4,4- diphenyl-3-buten-2-one oxime acetate was analyzed by semiempirical MNDO, AM1 and PM3 methods of calculation, assuming the process consists of three steps: thermal disrotatory electrocyclization of the oxime acetate, inversion of the cyclic intermediate on the nitrogen atom and elimination of acetic acid from the inverted intermediate according to Ei mechanism. It appears from PM3 calculations, which led to better results than MNDO or AM1, that the disrotatory electrocyclization is the rate-determining step for the whole synthesis.

3

Structure and Hydrogen Bonding of Solid N1-Alkyl-N2-(2-hydroxy, 4- or 5-methylphenyl)thioureas

Wawer I., Anulewicz-Ostrowska R., Maciejewska D., Koleva V.

Polish Journal of Chemistry

|

2000

|

Vol. 74, nr 6

823-835

EN

Crystalline N1-alkyl-N2-arylthioureas with ortho hydroxyl and para or meta methyl substituents to the phenyl ring were studied by single crystal X-ray diffraction, IR and solid state 13C cP MAS NMR. Two different modes of association were found: i) intermolecular N1H...S bonds and N2H not involved in hydrogen bonding in N1-methyl-N2-(2-hydroxy, 5-metylphenyl)thuiourea 1, ii) cyclic dimers with two N2H...S hydrogen bonds (S...N2 distance of 3.332 A) and N1H engaged in intermolecular N1H...O bond in N1-methyl-N2-(2-hydroxy,4 methylphenyl)thiourea 2. Changes of carbon chemical shifts between solution and solid state result mainly from the reorientation of the aromatic ring with respect to the thiourea fragent.

4

Prototropic Tautomerism in 2- and 4-Hydroxypyridines : Halogen Substituent Effects in the Gas Phase Calculated by Semiempirical (AM1) Method

Raczyńska E.

Polish Journal of Chemistry

|

1999

|

Vol. 73, nr 11

1863-1876

EN

Tautomeric equilibrium constants were calculated in the gas phase for unsubstituted, mono- and tetrahalogenated 4-hydroxypyridines and for unsubstituted, mono-, di- and tetrahalogenated 4-hydroxypyridines using semiempirical method. Influence of position of halogen on the pK is studied and compared with that found previously in solution.

5

Molecular structure of 5-chloro-2-[p-t-butylphenyl]benzoxazole : Relation between structure and antimicrobial activity of 2,5-disubstituted benzoxazoles

Mrozek A., Trzeźwińska H., Karolak-Wojciechowska J.

Polish Journal of Chemistry

|

1999

|

vol. 73 nr 4

625-633

EN

As part of our investigation on antimicrobial agents, the structure of 5-chloro-2[p-t-butylophenyl]benzoxazole is reported: C17h16ClNO, mol.mass 285.77, monoclinic, space group: C2/c; a=32.164(6) A, b=6.756(1) A, c=13.710(3) A; b=92.73(3)0, V=2975.8(10) A3; d=1.276 g cm-3; Z=8; F(000)=1200; m(CuKa)=2.219 mm-1. Final R=0.0658 for 2621 reflections with F>4s(F). Final atomic coordinates for this 2,5-disubstitued benzoxazole were used as a starting point in molecular modeling of remaining 32 derivatives eearched as antimicrobial agents. Electronic parameters calculated with quantum chemistry methods and classical Hansch's constants were applied in searching for structure-activity correlation. It was established that geometrical parameters (area and volume) and LUMO energy values seem to be most important for the activity.

6

The M(O2)X(YH3)3 dioxygen complexes (M=Rh, Co; X=F, Cl, Br, I; Y=N, P): an ab initio, DFT and semiempirical PM3(tm) study

Dobrowolski J. Cz., Jamróz M. H., Kazimirski J. K., Bajdor K., Borowiak M. A., Manna L., Miglietta M. L., Aresta M.

Polish Journal of Chemistry

|

1998

|

Vol. 72, nr 10

2205-2217

EN

The molecular structure, energetics and vibrations have been calculated for the MO2 moiety in the M(O2)X(YH3)3 series of metal dioxygen complexes at three levels of theory: ab initio (RHF/3-21G), DFT (B3PW91/3-21G) and semiempirical PM3(tm). The methods yielded the O-O distances consistent with the experimental values and similarly predicted the tendencies of geometrical parameters to change. The variation of the enthalpy of formation with the central metal atom, halogen and ligand seems to be in qualitative interconsistency, whereas changes in the MO2 moiety frequencies, found at different levels, disagree substantially.