Coordination properties of the bioligands creatinine and creatine in various reaction media

The coordination chemistry of guanidines and guanidinates

Abstract: Species containing the Y-shaped CN3 unit have recently attracted increasing attention as electronically and sterically flexible ligands. Neutral guanidines [(R2N)2CNR], guanidinates(−1) [(RN)2CNR2]− and guanidinates(2) [(RN)2CNR]2− are capable of exhibiting a variety of coordination modes and a range of donor properties leading to compatibility with a remarkably wide range of metal ions from all parts of the periodic table. The coordination chemistry of these species is reviewed up to July 2000, and aspects of their electronic structures and metal-ligand bonding characteristics discussed.

(Guanidine)copper complexes: structural variety and application in bioinorganic chemistry and catalysis

Abstract: Abstract In this paper, guanidine copper compounds are reviewed with an emphasis on structural characteristics and their application in bioinorganic chemistry and catalysis. The literature survey includes the copper coordination chemistry of biological guanidine derivatives, peralkylated guanidines including bicyclic ones and of further nitrogen-rich guanidine-type systems such as azoimidazoles, triazolopyrimidines and triaminoguanidines. From a sporadic interest dating back to the 1960s, research on this ligand class and its use in copper coordination chemistry has gained new impetus since 2000. With the synthesis of examples with sophisticated substitution at the characteristic CN3 framework, complex problems can be addressed in several fields of chemistry. This paper analyses the different types of guanidines for their special donor properties and highlights the specific advantages of guanidines as neutral donor ligands in copper coordination chemistry where a great variety of coordination modes was found. These compounds offer the ability to distribute the formal positive charge of the metal throughout the guanidine unit and represent more than simple σ-donating ligands.

A Fractional Bond Order of 1/2 in Pd25+−Formamidinate Species; The Value of Very High-Field EPR Spectra

Abstract: Reaction of Pd2(DAniF)4, 1, (DAniF = di-p-anisylformamidinate) with 1 equiv of AgPF6 in CH2Cl2 at or below −10 °C produces the paramagnetic species [Pd2(DAniF)4]PF6, 1-PF6, that has been studied by X-ray crystallography, UV−vis spectroscopy, electrochemistry, and multifrequency (9.5, 34.5, 110, and 220 GHz) EPR spectroscopy. Upon oxidation of the precursor, the Pd−Pd distance decreases by 0.052 A from 2.6486(8) to 2.597(1) A. The EPR spectra show broad signals with line widths of about 1000 G. The spectra collected at high field show a large spread of g tensor components (∼0.03), but these are masked at lower frequencies (9.5 and 34.5 GHz). A reinvestigation using high-field EPR of the p-tolyl analogue, which is the only other structurally characterized Pd25+ species (Cotton, F. A.; Matusz, M.; Poli, R.; Feng, X. J. Am. Chem. Soc. 1988, 110, 1144), shows that this species, which had been reported to give an isotropic 9.5 GHz EPR spectrum, also gives anisotropic 110 and 220 GHz EPR spectra with a similarly...

Fabrication of a disposable non-enzymatic electrochemical creatinine sensor

Abstract: A disposable non-enzymatic sensor for creatinine was developed by electrodepositing copper on screen printed carbon electrodes. The sensor was characterized using electrochemical and microscopic techniques. Electrochemical detection of creatinine was carried out in phosphate buffer solution of pH 7.4. The estimation was based on the formation of soluble copper-creatinine complex. The formation of copper-creatinine complex was established using the pseudoperoxidase activity of copper-creatinine complex. The sensor showed a detection limit of 0.0746 μM with a linear range of 6–378 μΜ. The sensor exhibited a stable response to creatinine and found to be free from interference from molecules like urea, glucose, ascorbic acid and dopamine. Real sample analysis was carried out with blood serum.

Binuclear Cu2+ complex mediated discrimination between L-glutamate and L-aspartate in water.

Abstract: L-Glutamate and L-aspartate selectivity is achieved by the action of two Cu2+ metal ions rightly disposed in a cyclophane-type macrocyclic framework; electrochemical sensing of glutamate has been achieved by adsorption of the copper complexes on graphite electrodes.

Cardiovascular activity of aromatic guanidine compounds.

Abstract: A series of aromatic guanidines and several 1-phenylbiguanides was prepared and tested for cardiovascular (CV) effects in anesthetized dogs measuring heart rate, blood pressure, carotid artery blood flow, and myocardial force changes. The predominant CV effect at minimally effective dose was vasoconstriction unassociated with cardiac stimulation. The structure-activity relationships of the compounds were discussed comparing their structural similarities to the beta-phenylethylamines. The most potent members of the series were phenylguanidines substituted in the 3 and 4 positions on the aromatic nucleus with hydroxy or chloro groups. Preliminary mechanism studies indicated that the 3,4-dihydroxyphenylguanidines act at least partially by a direct alpha-adrenergic mechanism

Crystal and molecular structure of creatininium tetrachlorocuprate(II)

Abstract: Preparation, crystal and molecular structure of creatininium tetrachlorocuprate(II) is described. The structure was solved by X-ray diffraction studies and was refined by least-squares methods to R = 0.041 for 1344 reflections. The compound is monoclinic, space group, P21/c. The unit cell parameters are a = 8.080(3), b = 7.831(2), c = 13.922(3) A, β = 113.77(2)°, V = 806.2 A3, dc = 1.786, dm = 1.77(1) g cm−3, Z = 2. The [CuCl4]2− ion is centrosymmetric and the copper atom is surrounded by four Cl atoms (CuCl1 2.233(1), CuCl2 2.268(1)) in a square planar arrangement. The creatininium cation is almost planar and each cation is linked to [CuCl4]2− units through hydrogen bonding involving the amino and imino nitrogen atoms.

Creatinine complexes of zinc, cadmium and mercury

Abstract: Zinc, cadmium and mercury(II) complexes of creatinine of the composition M(Creat) 2 X 2 (X = Cl, Br or I) are prepared. The complexes are characterized by analytical and spectral methods. The increase in cyclic NH stretching frequency in the case of complexes (3350 cm −1 ) from that of the free ligand (3300 cm −1 ) suggested that secondary nitrogen is involved in coordination. The shift in the resonances of cyclic NH proton in the 1 H NMR and carbonyl and imine carbons in 13 C NMR when compared to the ligand indicated that cyclic nitrogen coordinates. Conductivity measurements in N, N-dimethylformamide suggested that the complexes are non-electrolytes. Thermal decomposition behaviour of the complexes is also discussed.