Colin Gyles

Optosensing properties of fac-Re(CO)3(dpknph)Cl (dpknph=di-2-pyridyl ketone p-nitrophenyl hydrazone) toward chemotactic N-formylamino acids

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.

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.

Synthesis and physicochemical properties of fac-[Re(CO)3(κ2-N,N-dpkfah)Cl], dpkfah=di-2-pyridyl ketone 2-furoic acid hydrazone: the molecular structure of fac-[Re(CO)3(κ2-N,N-dpkfah)Cl] · acetone

Reaction between [Re(CO)5Cl] and di-2-pyridyl ketone 2-furoic acid hydrazone (dpkfah) (1) in refluxing toluene gave fac-[Re(CO)3(κ2-N,N-dpkfah)Cl] (2). Spectroscopic and electrochemical measurements disclosed sensitivity of 2 to its surroundings. 1H-NMR measurements showed that the amide proton exchanged with solvent protons, and its chemical shift is solvent and temperature dependent, while the chemical shifts of aromatic protons are solvent and temperature independent. Electronic absorption spectra of 2 divulged two intra-ligand charge transfer transitions (ILCT) in protophilic solvents and a single ILCT transition in non-protophilic solvents. Optical measurements on protophilic solutions of 2 established an equilibrium between 2 and its conjugate base, fac-[Re(CO)3(κ2-N,N-dpkfah-H)Cl]− (3). Thermo-optical measurements confirmed that the interconversion between 2 and 3 and gave ΔG ø values of −26.48 and 22.99 kJ mol−1, respectively, for the protonation of DMF and DMSO by 2. Optosensing measurements showed that [MCl2] (M = Zn, Cd, or Hg) in concentrations as low as 1.00 × 10−7 mol L−1 can be detected and determined using protophilic solutions of 2. Electrochemical measurements showed 2 to be more stable in CH3CN than DMF. Single-crystal X-ray structural analysis on fac-[Re(CO)3(κ2-N,N-dpkfah)Cl] · acetone (4) obtained from an acetone solution of 2 confirmed the solvent–complex interaction and revealed two symmetry-independent molecules in the asymmetric unit. The extended structure of 4 disclosed parallel stacks connected via a network of classic and non-classic hydrogen bonds.