Orville Green

Manganese carbonyl compounds of N,N-bidentate di-2-pyridylketone (dpk) and N,O,N-tridentate hydroxybis(2-pyridyl)methanolato (dpkO,OH). The structure of fac-[Mn(CO)3(dpkO,OH)]

Abstract Electrochemical measurements on fac -[Mn(CO) 3 (dpk)Br] and fac -[Mn(CO) 3 (dpkO,OH)] revealed solvent dependence and rich redox properties and X-ray studies on fac -[Mn(CO) 3 (dpkO,OH)] show distorted octahedral geometry around manganese with the major distortion is due to the binding of hydroxybis(2-pyridyl)methanolato (dpkO,OH) anion and anti-parallel tapes of fac -[Mn(CO) 3 (dpkO,OH)] interlocked via a network of hydrogen bonds. When di-2-pyridyl ketone (dpk) was allowed to react with [Mn(CO) 5 Br] in dry diethyl ether under ultrasonic conditions fac -[Mn(CO) 3 (dpk)Br] was isolated in good yield and when the same reaction was carried out under reflux conditions in toluene fac -[Mn(CO) 3 (dpkO,OH)] was isolated. Infrared spectra of the isolated compounds confirmed their fac -geometry and the presence and absence of the ketonic group of dpk. Electrochemical measurements on fac -[Mn(CO) 3 (dpk)Br] reveal sensitivity to solvents and the presence of reversible and irreversible electronic transfers. In contrast to fac -[Re(CO) 3 (dpk)Cl] where noteworthy electrochemical reactions with CO 2 were observed, the electrochemical reactions of CO 2 with fac -[Mn(CO) 3 (dpk)Br] disclosed no significant reaction. However, when fac -[Mn(CO) 3 (dpk)Br] was allowed to electrochemically interact with group I and II metal ions considerable electrochemical changes were noted on the second reduction wave that may point to the possible use of fac -[Mn(CO) 3 (dpk)Br] as an electrochemical sensor for group I and II metal ions. The electrochemical properties of fac -[Mn(CO) 3 (dpkO,OH)] show the presence of closely spaced irreversible oxidations and probable electrochemical oxidation of coordinated dpkO,OH anion to dpk in dmf. Crystals of fac -[Mn(CO) 3 (dpkO,OH)] obtained from dimethyl sulfoxide (dmso) solution of fac -[Mn(CO) 3 (dpkO,OH)] are in the monoclinic C2/c space group. Structural analysis on fac -[Mn(CO) 3 (dpkO,OH)] disclosed distorted octahedral coordination about manganese with the major distortion due to the tridentate coordination of dpkO,OH anion and the packing of molecules show stacks of anti-parallel tapes of fac -[Mn(CO) 3 (dpkO,OH)] interlocked via a network of hydrogen bonds.

Synthesis, spectroscopy, thermodynamics and structure of [ZnCl2 (η3-dpktch)] (η3-dpktch = N,N,O- di-2-pyridyl ketone thiophene-2-carboxylic acid hydrazone)

When dpktch was reacted with ZnCl2 in refluxing acetonitrile in air [ZnCl2(η3-dpktch)] was isolated in good yield. Infrared spectra suggest weaker binding of dpktch in [ZnCl2(η3-dpktch)] than in [CdCl2(η3-dpktch)]. 1H-NMR studies in non-aqueous media show that [ZnCl2(η3-dpktch)] is sensitive to changes in its environment and exchanges its amide proton. Electronic absorption spectral measurements confirmed the sensitivity of [ZnCl2(η3-dpktch)] to changes in its surroundings and show inter-conversion between two intra-ligand-charge-transfer transitions (ILCT) at 330 ± 2 nm and 404 ± 2 associated with [ZnCl2(η3-dpktch)] and its conjugate base. Thermo-optical measurements in non-aqueous dmf and dmso show facile inter-conversion between [ZnCl2(η3-dpktch)] and its conjugate base, respectively. Also, it is shown that protonation of dmf by [ZnCl2(η3-dpktch)] is exothermic (standard enthalpy of protonation ΔHθ  = −40.7 ± 1.8 kJ mol−1), but endothermic for dmso (ΔHθ  = +8.3 ± 1.5 kJ mol−1). Chemical stimuli in concentrations as low as 5.0 × 10−7 M can be detected and determined using [ZnCl2(η3-dpktch)] in non-aqueous media. X-ray crystallographic studies on a monoclinic, P21/n single crystal of [ZnCl2(η3-dpktch)] confirmed the N,N,O-coordination of dpktch and revealed interdigitated units of [ZnCl2(η3-dpktch)] connected via a web of hydrogen bonds.

Synthesis and structure of the first molybdenum compound of N,O,N-hydroxybis(2-pyridyl)methanolato (η 3-dpkO, OH). The structure of [Mo(O)2(μ-O)(η 3-dpkO,OH)]2 · 2dmso

When di-2-pyridyl ketone (dpk) was allowed to react with [Mo(CO)6] in toluene under reflux in air [Mo(O)2(μ-O)(η 3-dpkO,OH)]2 where η 3-dpkO,OH is N,O,N-hydroxybis(2-pyridyl)methanolato was isolated. Infrared and 1H-NMR spectral data measured on solutions of the isolated compound indicate the absence of the carbonyl groups and the presence of coordinated η 3-dpkO,OH, terminal and bridging oxo-groups and elemental analysis confirmed the formulation of the product as [Mo(O)2(μ-O)(η 3-dpkO,OH)]2. Crystals of [Mo(O)2(μ-O)(η 3-dpkO,OH)]2·2dmso obtained from a dimethyl sulfoxide (dmso) solution of [Mo(O)2(μ-O)(η 3-dpkO,OH)]2 are in the monoclinic P21/c space group. X-ray structural analysis confirmed the identity of [Mo(O)2(μ-O)(η 3-dpkO,OH)]2 and shows a dioxomolybdenum oxo-bridged dimer with two terminal oxygen atoms and one tridentate N,O,N-dpkO,OH occupying the coordination sites of the high-valent molybdenum(VI) in a pseudo-octahedral coordination geometry. The molecular packing shows parallel stacks of [Mo(O)2(μ-O) (η 3-dpkO,OH)]2·2dmso and disclose an extensive network of non-covalent interactions within each stack.

Molecular sensing behavior of di-2-pyridyl ketone p-aminophenylhydrazone hydrate (dpkabh·H2O) in non-aqueous media

(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.

Nuclear magnetic resonance and optosensing properties of di-2-thienyl ketone p-nitrophenylhydrazone (DSKNPH) in non-aqueous media

The compound di-2-thienyl ketone p-nitrophenylhydrazone (DSKNPH) melting point 168-170 degrees C was isolated in good yield from the reaction between di-2-thienyl ketone (DSK) and p-nitrophenylhydrazine in refluxing ethanol containing a few drop of concentrated HCl. Nuclear magnetic resonance studies on DSKNPH in non-aqueous solvents revealed strong solvent and temperature dependence due to solvent-solute interactions. Optical measurements on DSKNPH in DMSO in the presence and absence of KPF(6) gave extinction coefficients of 83,300+/-2000 and 25,600+/-2000M(-1)cm(-1) at 612 and 427nm at 295K. In CH(2)Cl(2), extinction coefficient of 34,000+/-2000M(-1)cm(-1) was calculated at 422nm. When DMSO solutions of DSKNPH were allowed to interact with DMSO solutions of NaBH(4) the low energy electronic state becomes favorable and when DMSO solutions of DSPKNPH where allowed to interact with DMSO solutions of KPF(6) or NaBF(4), the high energy electronic state becomes favorable. The reversible BH(4)(-)/BF(4)(-) interconversion points to physical interactions between these species and DSKNPH and hints to the possible use of DSKNPH as a spectrophotometric sensor for a variety of physical and chemical stimuli. Thermo-optical measurements on DSKNPH in DMSO confirmed the reversible interconversion between the high and low energy electronic states of DSKNPH and allowed for the calculations of the thermodynamic activation parameters of DSKNPH. Changes in enthalpy (DeltaH(slashed circle)) of +57.67+/-4.20; 27.15+/-0.90kJmol(-1), entropy (DeltaS(slashed circle)) of +160+/-12.88; 83+/-2.91Jmol(-1) and free energy (DeltaG(slashed circle)) of -8.52+/-0.40; 2.66+/-0.25kJmol(-1) were calculated at 295K in the absence and presence of NaBH(4), respectively. Manipulation of the equilibrium distribution of the high and low energy electronic states of DSKNPH allowed for the use of these systems (DSKNPH and surrounding solvent molecules) as molecular sensors for group I and II metal ions. Group I and II metal ions in concentrations as low as 1.00x10(-5) M can be detected and determined using DSKNPH in DMSO.