Stefan S. Kurek

The synthesis and electrochemistry of a novel ferrocene bis-porphyrin molecule

Abstract The synthesis and electrochemistry of a new ferrocene bis-porphyrin molecule ( 3 ) derived from 1,1′-bis(chlorocarbonyl)ferrocene and 5-( p -hydroxyphenyl)-10,15,20-triphenylporphyrin are reported. High field 1 H NMR data indicate the respective porphyrin macrocyclic rings of 3 are in a gauche type conformation.

Syntheses of 4-benzyl-3,5-dimethylpyrazolylborato complexes of molybdenum and tungsten nitrosyls: molecular structure of [Mo(CO)2(NO){HB(3,5-Me2-4-PhCH2C3N2)3}], a complex with an ‘inverted’ bowl-like structure

Reaction of [HB(bdmpz)3]–, obtained by reaction of 4-benzyl-3,5-dimethylpyrazole (Hbdmpz) with KBH4, with [M(CO)6](M = Mo or W) and p-MeC6H4SO2N(NO)Me afforded [M(CO)2(NO)-{HB(bdmpz)3}](M = Mo or W). The molybdenum carbonyl was converted into [Mo(NO)-{HB(bdmpz)3}X(Y)](X = Y = Cl, I or OC6H4Me-p; X = Cl, Y = OMe or OC6H4Me-p) the spectral and electrochemical properties of which are virtually identical to those of [Mo(NO){HB(dmpz)3}X(Y)](Hdmpz = 3,5-dimethylpyrazole), indicating that the addition of a benzyl group has no significant electronic effect in the new species. However, a crystal and molecular structure determination of [Mo(CO)2(NO){HB(bdmpz)3}] revealed that the molecule has a highly symmetrical structure, the CH2groups of the benzyl groups in the tris(pyrazolyl)borate ligand being disposed in a star-shaped configuration where the phenyl rings adopt an ‘inverted’ bowl-like structure with the BH group inside and the Mo(CO)2(NO) group outside the bowl. The arrangement of the 4-benzyl groups with respect to the pyrazolyl rings and the H–B ⋯ Mo three-fold axis is strongly reminiscent of an inverted three-legged ‘Isle of Man’ symbol.

A novel porphyrin-ferrocene-quinone linked molecule

The synthesis and electrochemistry are reported of a new porphyrin-ferrocene-quinone linked molecule (6) prepared in a stepwise procedure from 1,1′-bis(chlorocarbonyl)ferrocene (1), 5-(p-hydroxyphenyl)-10,15,20-triphenylporphyrin (2), and 2-hydroxynaphthoquinone (3).

Optically resolved 1-methylbenzylamido complexes of molybdenum and tungsten, and the crystal and molecular structure of s-iodo{tris (3,5-dimethylpyrazolyl)borato} {(+)-1-phenylethylamido}nitrosylmolybdenum, s-[Mo(NO){HB(3,5-Me2C3HN2)3} I{(+)-NHCH(Me)Ph}]

Abstract [M(NO)L*X2][M = Mo or W;L* = hydridotris(3,5-dimethylpyrazolyl)borate; X = Cl (Mo, W), X = I (Mo)] reacted with (+)- and (−)-1-phenylethylamine, NH2CH (Me)Ph, affording diastereomeric mixtures of [M(NO)L* X(NHCHMePh)]. These were separated by chromatography, and the structure of the pure diastereomer obtained by reaction of [Mo(NO)L*I2] with (+)-NH2CHMePh was determined crystallographically. The absolute configuration of this compound, [Mo(NO)L* I{(+)-NHCHMePh}], was determined to be S.

New paramagnetic pyrazole complexes of tris(3,5-dimethylpyrazolyl)borato molybdenum nitrosyl chloride and iodide and the structure of [Mo(NO){HB(3,5-Me 2 C 3 HN 2 ) 3 }Cl(3,5-Me 2 C 3 HN 2 H)]

Abstract Reduction of [Mo(NO)L*Cl2][L* = HB(3,5-Me2C3HN2)3] with n-butyl lithium in the presence of SnBun3Cl afforded the paramagnetic (17-electron) [Mo(NO)L*Cl(3,5-Me2C3HN2H)] (1). Related compounds, [Mo(NO)L*XQ] (Q = pyrazole, 3,5-dimethyl-pyrazole, 4-bromopyrazole and 4-bromo-3,5-dimethylpyrazole; X = Cl or I), were prepared by the reduction of [Mo(NO)L*X2] by Q (X = I) or by n-butyl lithium in the presence of Q (X = Cl). IR and EPR spectroscopic characterization of these species is reported and the X-ray structure of [Mo(NO)L*Cl(3,5-Me2C3HN2H)]· 1 2 CH2Cl2, in which the molybdenum atom has octahedral coordination with disordered Cl and NO ligands, is described.

Intramolecular electron transfer in peripherally metallated tetraphenyl porphyrin derivatives containing molybdenum mononitrosyl redox centres

Picosecond laser spectroscopy measurements on the novel complexes [Mo(NO)(L)Cl(Etpp)][Etpp = 5-(E-substituted phenyl-10,15,20-triphenylporphyrin; L = hydrotris(3,5-dimethylpyrazol-1-yl)borate, E =para-O, meta-O, ortho-O; para-NH] indicate that the observed fluorescence quenching in these compounds is due to fast (τ < 30 ps) intramolecular charge separation to produce transient species with lifetimes in the range 120–290 ps.

Puzzling Aqueous Solubility of Guanine Obscured by the Formation of Nanoparticles

Dissolution of guanine in neutral solutions was obscured by peculiar behavior of guanine, indicating an apparent dependence of solubility on the amount of solid guanine used. Here, we demonstrate that the problem is caused by the formation of tiny guanine nanoparticles that tend to grow forming stable particles of ca. 800 nm size. This effect can be minimalized by using small quantities of guanine powder for dissolution. We also show that assuming a constant, independent of pH, concentration of neutral form of guanine, at 25 °C equal 25.4 μM, and applying known p Ka values related to its dissociation or protonation, it is possible to calculate the concentrations of all conjugate acids and bases of guanine at the given pH value, and by summing them up, the guanine solubility.

Synthesis and structural characterisation of glucofuranoside and galactopyranoside derivatives of [tris(3,5-dimethylpyrazolyl)borato]-molybdenum and -tungsten nitrosyls

The complex [M(NO)L*X2][L*= tris(3,5-dimethylpyrazolyl)borate; M = Mo, X = Cl or l; M = W, X = Cl] reacted with 1,2:5,6-di-O-isopropylidene-D-glucofuranose (HGf) and with 1,2:3,4-di-O-isopropylidene-D-galactopyranose (HGp) to give diastereomers of [M(NO)L*(X)Gf] and [M(NO)L*(X)Gp]. The structure of the thermodynamically stable diasteromer of [Mo(NO)L*(I)Gf] was determined by a single-crystal X-ray diffraction study, which showed the absolute configuration at the Mo atom to be S, in agreement with the known configuration of the mentholate R-[Mo(NO)L*(Cl){(–)-OC10H19}] and the circular dichroism (CD) spectra. The absolute configurations of the other isolated diastereomers were related to this complex and to R-[Mo(NO)L*Cl{(–)-OC10H19}] by comparison of their CD spectra.

Tris(3,5-dimethylpyrazolyl)borato molybdenum and tungsten nitrosyl mentholates

The complex [M(NO)L*X2][L*= tris(3,5-dimethylpyrazolyl)borate; M = Mo, X = Cl or I; M = W, X = Cl] reacted with (+)- and (–)-menthol (C10H19OH) affording diastereomeric mixtures of [M(NO)L*(X)(OC10H19)]. These were separated by chromatography, and the structure of the diastereomer [Mo(NO)L*(Cl){(–)-OC10H19}] determined crystallographically. The absolute configuration at the metal in this compound was determined to be R, and those of all other complexes [M(NO)L*(X)(OC10H19)] related to it by comparison of their circular dichroism spectra.