RESUMO
(1)H NMR studies on di-2-pyridyl ketone p-aminobenzoylhydrazone hydrate (dpkabh.H(2)O) in non-aqueous solvents show high sensitivity to its surrounding. In protophilic solvents (d(6)-dmso or d(7)-dmf), the amine protons are equivalent, while in CDCl(3) they are not. Variable temperature analysis in CDCL(3) show the NH proton to exhibit high temperature dependence due to strong intra-molecular hydrogen bonding of the type N-H...N between the amide (NH) and N atom of a pyridine ring. The temperature dependence for the same proton in d(6)-dmso and d(7)-dmf is due to hydrogen bonding of the type N-H...O between the amide proton and oxygen atom of the solvent. Optical measurements on dpkabh.H(2)O show one intra-ligand charge transfer (ILCT) transition in CH(2)Cl(2) and in protophilic solvents, two ILCT of the donor-acceptor type due to dpkabh.H(2)O and its conjugate base appeared. Variable temperature studies on protophilic solution of dpkabh.H(2)O confirm the sensitivity of dpkabh.H(2)O to its surroundings and show facile reversible inter-conversion between dpkabh.H(2)O and its conjugate base. Changes in enthalpy (DeltaH(phi)) of -5.2+/-0.4 and -24.2+/-1.20 kJ mol(-1), entropy (DeltaS(phi)) of +9.6+/-0.5 and -63.0+/-2.0 JK(-1) mol(-1), and free energy (DeltaG(phi)) of +2.3+/-0.2 and +5.4+/-0.2 kJ mol(-1) were calculated for dpkabh.H(2)O at 298 K in dmso and dmf, respectively. When stoichiometric amounts of NaBH(4) or MCl(2) (M=Zn, Cd or Hg) were added to protophilic solution of dpkanh.H(2)O conversion from the high to low energy electronic transition was observed and show that substrates in low concentrations can be detected and determined using protophilic solution of dpkabh.H(2)O.
Assuntos
Hidrazonas/química , Piridinas/química , Solventes/química , Ácidos/química , Álcalis/química , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Análise Espectral , Temperatura , TermodinâmicaRESUMO
A new polymorph of di-2-pyridyl ketone 4-nitrophenylhydrazone [alternative name: N-(dipyridin-2-ylmethylene)-N'-(4-nitrophenyl)hydrazine], C17H13N5O2, isolated from the filtrate of a sonicated acetonitrile solution of dpknph and CdCl2, was found to crystallize in the monoclinic space group P21/c, in contrast to the known form which crystallizes in P21/n. The non-coplanar molecules pack in parallel stacks without any intermolecular hydrogen-bonding interactions. This packing pattern contrasts with the interlocked interdigitated packing seen in the previously known polymorph.
RESUMO
Mikanolide [systematic names: 1,10:2,3-diepoxy-6,8-dihydroxy-11-vinylgermacr-4-ene 12,14-di-gamma-lactone and 7,10a-dimethyl-1a,1b,2a,6a,7,9a,10,10a-octahydro-4H-6,3-methenofuro[3,2-c]bisoxireno[f,h]oxacycloundecin-4,8(6H)-dione], C(15)H(14)O(6), derived from a variety of Mikania micrantha growing in Portland, Jamaica, contains a methylcyclodecane ring fused to an unsaturated planar alpha,gamma-lactone, an envelope-type near-planar vinyl-beta,gamma-lactone and two epoxide moieties. The crystal packing shows stacks of mikanolide molecules interlocked via a network of non-classical C-H...O hydrogen bonds between the lactone units.
Assuntos
Estrona/análogos & derivados , Estrona/química , Lactonas/química , Mikania/química , Anti-Infecciosos/química , Antineoplásicos Fitogênicos/química , Cristalografia por Raios X , Ligação de Hidrogênio , Jamaica , Modelos Moleculares , Conformação Molecular , Sesquiterpenos de GermacranoRESUMO
Optical measurements on fac-Re(CO)(3)(dpknph)Cl in polar non-aqueous solvents in the presence and absence of NaBH(4)/KPF(6) revealed reversible interconversion between the high (beta-) and low (alpha-) energy electronic states of fac-Re(CO)(3)(dpknph)Cl. The reversibility of these interactions and the disturbance of the equilibrium distribution of the low (alpha-) and high (beta-) energy electronic state upon addition of NaBH(4)/KPF(6) mark improvement in the optosensing properties of fac-Re(CO)(3)(dpknph)Cl. The optical behavior of fac-Re(CO)(3)(dpknph)Cl in the presence and absence of the l-methionine and chemotactic N-formylamino acids: N-formyl-l-methionine (NFM), N-formyl-l-glycine (NFG) and N-formyl-l-phenylalanine (NFP) shows the alpha- and beta-electronic states of fac-Re(CO)(3)(dpknph)Cl to be insensitive to l-methinonine and highly sensitive to N-formylamino acids. N-formylamino acids in concentrations <1.0x10(-5) M can be determined using the optical sensor fac-Re(CO)(3)(dpknph)Cl in non-aqueous polar solvents. The optosensing power of fac-Re(CO)(3)(dpknph)Cl towards N-formylamino acids depends on the concentration and polarity of the side chain of the amino acids and increases in the following order: NFM>NFG>NFP.