Biguanide Complexes Research Articles

Synthesis, Characterization and Structural Analysis of Two New Biguanide Complexes

This study reports on the synthesis and characterization of two new coordination compounds of the active pharmaceutical ingredient metformin and transition metals. The cobalt compound with the formula [Co(Met)3][CoCl4]Cl·3H2O is a complex salt formed by a cationic Co(III) octahedral and anionic Co(II) tetrahedral subunits. The Cu(II) complex is represented by the formula [(Cu(Met)Cl)2-μ-Cl2] and is a dimeric compound with two chloride anions acting as a bridge, forming shared-edge square pyramidal units. Both compounds were characterized by single crystal X-ray diffraction, FT-IR spectroscopy and thermal analysis.

Directional Construction of New Nonlinear Optical Bifunctional Units through Molecular Engineering Design Inspired by the B3O7-Typed Configuration.

Studies on new functional structural units with both large hyperpolarizability and high anisotropy are essentially important for finding high-performance nonlinear optical (NLO) materials and enriching the material systems. Under the guidance of the "structure-analogue" strategy, the work utilizes the molecular engineering approach to direct the construction of target units, BC2N5O2 and B(C2N5)2 units. The BC2N5O2 unit with a highly analogous structure to the B3O7 group and its derivate B(C2N5)2 unit with a configuration of B5O10 group are designed as NLO-active units. Furthermore, two compounds with these new NLO-active units, BC2N5H6(OH)2·H2O (I) and B(C2N5H6.5)2(NO3)2 (II), are synthesized, successfully. These compounds exhibit excellent properties with second-harmonic generation (SHG) responses ranging from 0.5 to 5.9 times that of KDP and large birefringence (ΔnI = 0.181 @ 546.1 nm and ΔnII = 0.148 @ 546.1 nm). Theoretical calculations prove that the BC2N5O2 and B(C2N5)2 units make great contributions to the SHG effects and birefringence, which confirms that the BC2N5O2 and B(C2N5)2 units are novel NLO bifunctional units and could be excellent fundamental building blocks to construct amounts of novel NLO and birefringence crystals. Our studies would enlighten the research studies on biguanide complexes of boron.

P-012 - 99mTc/Re tricarbonyl biguanide complexes for cancer theranostics

P-012 - 99mTc/Re tricarbonyl biguanide complexes for cancer theranostics

Supported Palladium Catalysis Using a Biguanide N-Donor Motif on Mesoporous Silica for Suzuki-Miyaura Coupling Reaction

A supported Pd(II)/biguanide complex on ordered mesoporous SBA-15 material (Pd@SBA-15/Met) exhibited catalytic activity in the cross-coupling reaction. The structural and surface characteristics of the prepared catalysts were investigated by various techniques (XRD, SEM, FT-IR and AAS). The catalytic performance of the catalysts was evaluated in Suzuki-Miyaura coupling reaction and it was proved to act as a recoverable catalyst in green media with excellent reactivity combined with recyclability.

Reductions of oxo species by aquatitanium(ii) as catalyzed by titanium(iv)

Titanium(II) solutions, prepared by dissolving titanium wire in triflic acid + HF, contain equimolar quantities of Ti(IV). These preparations react readily with oxidizing species such as VO(2)(+), substituted benzoquinones, and the biguanide complex of Mn(IV). Reactions with excess Ti(II) yield Ti(III). Reductions of 1,4-benzoquinones and the Mn(IV) complex are catalyzed by added Ti(IV) but stoichiometry is unaffected. Rate laws for the Ti(IV)-catalyzed reactions are consistent with formation of a Ti(II)-Ti(IV) complex (K(formation) 4 x 10(2) M(-1)), which, in some cases, also partakes in contributing deprotonated and halogen-catalyzed paths.

On mononitrosylcobalt(biguanidinium) complexes

A new six-coordianted mononitrosylcobalt(III)BiguanidE complex. [Co(BigH + ) 2 (NO - )H 2 O] 2 + SO 4 .1.5H 2 O (where, BigH + = C 2 N 5 H 7 ), has been prepared by passing pure NO gas through the methanolic suspension of the freshly prepared bis(biguanidinium)coblat(II) sulphate, [Co(BigH + ) 2 ]SO 4 .4H 2 O, in nitrogen atmosphere. The structure of the complex and bonding of the ligand have been suggested from magnetic, electronic and IR spectral data. The NO is bonded to the metal atom as NO - ion and the complex is feebly paramagnetic. The slight magnetic moment value of the complex is attributed to the T.I.P. contribution of mixing of ground leve 1 A 1 g term with higher energy level term. The sulphate is ionic and one water molecule is bonded to the metal atom, which completes coordination number six of the cobalt(III) atom.

Vanadyl–biguanide complexes as potential synergistic insulin mimics

Vanadium has well-documented blood-glucose-lowering properties both in vitro and in vivo. The design of new oxovanadium(IV) coordination compounds, intended for use as insulin-enhancing agents in the treatment of diabetes mellitus, can potentially benefit from a synergistic approach, in which the whole complex has more than an additive effect from its component parts. Biguanides, most importantly metformin, are oral hypoglycemic agents used today to treat type 2 diabetes mellitus. In this study, biguanide, metformin, and phenformin, all biguanides, were coordinated to oxovanadium(IV) to form potential insulin-enhancing compounds. Highly colored, air-stable, bis(biguanidato)oxovanadium(IV), [VO(big) 2], bis( N′,N′-dimethylbiguanidato)oxovanadium(IV), [VO(metf) 2], and bis(β-phenethylbiguanidato)oxovanadium(IV), [VO(phenf) 2], were prepared. Solvation with dimethylsulfoxide occurred with VO(metf) 2 to form a six-coordinate complex. Precursor ligands and oxovanadium(IV) coordination complexes were characterized by infrared spectroscopy, mass spectrometry, elemental analyses, magnetic susceptibility, and, where appropriate, 1H NMR spectroscopy. Biological testing with VO(metf) 2, a representative compound, for insulin-enhancing potential included acute (72 h) administration, both by intraperitoneal (i.p.) injection and by oral gavage (p.o.) in streptozotocin (STZ)-diabetic rats. VO(metf) 2 administration resulted in significant blood-glucose lowering at doses of 0.12 mmol kg −1 i.p. and 0.60 mmol kg −1 p.o. (previously established as ED 50 doses for organically chelated oxovanadium(IV) complexes); however, no positive associative effects due to the presence of biguanide in the complex were apparent.

A Triply Hydrogen-Bonding System Constructed by Self-Assembly of Biguanide Complex and Imide-Containing Compound

Abstract A triply hydrogen-bonding system has been constructed between bis(biphenylbiguanidado)nickel(II) ([Ni(bpbg)2]) and phenobarbital (Phbar), which has been characterized by the IR and 1H-NMR spectroscopies and the X-ray structure analysis.

The structure of biguanide complexes of boron

Biguanide complexes of boron have been investigated as potential exterior grade fixed boron wood preservatives. Two biguanide rings are necessary for achieving moderate hydrolytic stability in application to wood. The complexes B(big)(OH) 2 ( 1) and B(big) 2Cl ( 2) (big = biguanide) have been investigated by 11B and 13C NMR spectroscopy and their structures determined by X-ray crystallography.

Kinetics and mechanism of dissociation of copper(II) complexes of biguanide and someN 1-substituted biguanides in aqueous acetate buffer media

The kinetics fo dissociation of thebis complexes [Cu(LH)2]2+ formed by CuII with biguanide andN 1-substituted methyl, phenyl, dimethyl and diethyl biguanides into the mono biguanide complexes in aqueous NaOAc-HOAc buffer media have been studied by stopped-flow spectrophotometry. The results, under pseudo-first-order conditions, indicate kobs=ko+kH[H+]. For the different complexes ko values are comparable, but kH values differ appreciably; log kH versus log K d H is linear withca. unit slope K d H being the equilibrium constant for the process: $$[{\text{Cu(LH)}}_{\text{2}} ]^{2 + } + 2{\text{H}}_{\text{2}} {\text{O}} + {\text{H}}^{\text{ + }} \rightleftharpoons [{\text{Cu(LH)(H}}_{\text{2}} {\text{O)}}_{\text{2}} ]^{2 + } + {\text{LH}}_{\text{2}}^{\text{ + }}$$ Based on these observations and from consideration of ΔH‡ and ΔS‡ values, we propose and associative mechanism, with significant bond formation by the incoming H2O in the Ko path, and a dissociative mechanism for the kH path.

Chromatographic Studies of Metal Complexes. Part-lll. Adsorption, Dissociation, and Intermediate Complex Formation of some Square-planar Biguanide Complexes of Copper(II), Nickel(II) and Palladium(II) on Silica Gel

Chromatographic Studies of Metal Complexes. Part-lll. Adsorption, Dissociation, and Intermediate Complex Formation of some Square-planar Biguanide Complexes of Copper(II), Nickel(II) and Palladium(II) on Silica Gel

An EPR study of copper(II)-substituted biguanide complexes. Part III

The EPR and optical spectra of bis(diethylbiguanide)copper(II) base and its salts and mono(diethylbiguanide)copper(II) salts have been measured both in the solid state and in N,N-dimethylformamide (DMF) in order to elucidate the structure and nature of the bonding between the central metal atom and the ligand. From the spectral data the degree of covalency of σ- and π-bonds of the copper(II) ion with the nitrogen atoms of the ligands have been calculated. The σ-bonds present a moderate degree of covalence while the in-plane π-bonds possess a strong covalent character. The covalency of the biguanide complexes is attributed to the strong σ-interaction of the copper(II) ion with deprotonated imino ligand bonding sites and electron delocalization over the chelate ring. The superfine structure of some compounds may be ascribed to the interaction of the unpaired electron of the copper(II) ion with four equivalent or nearly equivalent nitrogen atoms of the ligands. The general properties of the complexes studied, which contain the equivalent CuN 4 2− chromophore, are summarized.

FIA determination of chlorhexidine by means of the precipitation with Cu(II)

The determination of chlorhexidine in pharmaceutical formulations is carried out using flow injection analysis (FIA) with measurement by atomic absorption spectrometry (AAS). The method is based on the formation of a copper—biguanide complex precipitate when the sample is injected into an ammoniacal copper solution. The precipitate is retained on a plastic or paper filtering device. A nitric acid stream dissolves the precipitate and carried the Cu(ll) to the AAS detector. The chlorhexidine is determined over the range 5–20 ppm. The influence of interfering substances is investigated.

Kinetics and mechanisms of the reactions of unsymmetrical chelate complexes. Acid-catalyzed aquation of glycinatobis-(biguanide)cobalt(III) perchlorate

Abstract The presence of the unsymmetrical glycinato chelate in this complex, makes the positions of the two biguanides non-equivalent. Thus the acid-catalyzed dissociation of one or other of them, gives two different isomeric (α- and β-) diaquo- products. Up to ∼50°C, the dissociation of only one biguanide takes place with the formation of the α- diaquo product. The α- diaquo form isomerizes to the β- form at higher temperature. Direct formation of the β- form does not take place at any stage of the reaction. Aquation of the bis(biguanide) complex follows a dissociative pathway up to ∼50°C, above which it becomes a complicated one. Isomerization of the α- product takes place intramolecularly by two paths, one dependent and the other independent of acid concentration. Both the isomerization paths involve “bond-rupture” processes.

Mechanistic studies on six-membered chelate complexes. Aquation of some dichlorobis(substituted biguanide)rhodium(III) nitrates

Studies on the aquation of dichlorobis(substituted biguanide)rhodium(III) complexes were carried out in aqueous and aqueous methanol media by conductometric method. The release of chlorides in all the complexes takes place in a steppe manner and rates of each step were determined by a graphical method. Rates of aquation decrease with any substituent and remain nearly equal for all the substituents for both steps. Inductive effect does not seem to be responsible as it changes very little with substitution. In aqueous methanol, rates decrease with increased percentage of methanol for the unsubstituted biguanide complex, but the reverse is true for the phenyl substituted complex. This is due to the greater solvation of phenyl complex in the organic enriched solvent. From various factors it was indicated that the probability of bond formation in the transition state is greater with substituted complexes.

Transition metal complexes of amidinourea and related ligands part III. Infrared spectra and thermal decomposition studies on metal complexes of O-alkyl-1-amidinoureas

The i.r. spectral data on O-methyl-l-amidinourea hydrochloride,O-ethyl-1-amid inourea hydrochloride and the metal complexes [M = copper(H), nickel(II), palladium(II), zinc(II) and oxovanadium(IV)] ofO-methyl-l-amid inourea andO-ethyl-l-amidinourea are reported. The spectral results suggest that secondary amine nitrogens are the donor atoms inO-alkyl-1-amid inourea. The free ligands and the complexes exhibit a characteristic band at ca. 1100 cm−1 due to the C-OR group. The i.r. and electronic spectral data on the hydrated and anhydrous uncharged metal complexes indicate that the hydrated uncharged metal complexes ofO-alkyl-l-amidinourea may be represented as [M(AAU)n]] · xH20 and not as [M(AAUII)n](OH)n · xH2O [where AAU = H2NC(=NH)NC(=NH)OR and AAUH = H2NC(=NH)NHC(=NH)OR, R = Me, Et]. The use of the term “anhydrobase” is confusing and suitable names for various metal complexes ofO-alkyl-l-amid inourea are suggested. The main decomposition stage in metal complexes ofO-ethyl-l-amidinourea occurs at lower temperatures than for the corresponding biguanide complexes indicating that the former are less stable than the latter.

Biguanide and ethylenedibiguanide complexes of ruthenium

Biguanide and ethylenedibiguanide complexes of ruthenium

Electronic and infrared spectra of biguanide complexes of the 3 d-transition metals

The electronic and i.r. spectra of the complex biguanide bases of V, Cr, Mn, Co, Ni, Cu and Zn are studied and assignments of the chief bands are made. Spectral data conform to distorted octahedral structures for the V, Cr, Mn and Co complexes, square planar structures for Ni and Cu and a tetrahedral configuration for Zn.

ChemInform Abstract: THERMAL DECOMPOSITION OF THE BIGUANIDE COMPLEXES OF THE 3D‐TRANSITION METALS (V, CR, MN, CO, NI, CU AND ZN)

Chemischer InformationsdienstVolume 5, Issue 20 Organoelement Compounds ChemInform Abstract: THERMAL DECOMPOSITION OF THE BIGUANIDE COMPLEXES OF THE 3D-TRANSITION METALS (V, CR, MN, CO, NI, CU AND ZN) P. V. BABYKUTTY, P. V. BABYKUTTYSearch for more papers by this authorP. INDRASENAN, P. INDRASENANSearch for more papers by this authorR. ANANTARAMAN, R. ANANTARAMANSearch for more papers by this authorC. G. RAMACHANDRAN NAIR, C. G. RAMACHANDRAN NAIRSearch for more papers by this author P. V. BABYKUTTY, P. V. BABYKUTTYSearch for more papers by this authorP. INDRASENAN, P. INDRASENANSearch for more papers by this authorR. ANANTARAMAN, R. ANANTARAMANSearch for more papers by this authorC. G. RAMACHANDRAN NAIR, C. G. RAMACHANDRAN NAIRSearch for more papers by this author First published: May 21, 1974 https://doi.org/10.1002/chin.197420382AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume5, Issue20May 21, 1974 RelatedInformation

Thermal decomposition of the biguanide complexes of the 3d-transition metals

The thermal decomposition (TG, DTG and DTA) of the complexes of biguanide with the following metals was studied: V, Cr, Mn, Co, Ni, Cu and Zn. Structural water, when present, is first eliminated at ∼100–150°C; this is followed by a main decomposition state at ∼300–350°C. Pyrolytic residues are analysed and characterised by their x-ray powder diffraction patterns and are found to be the oxides V 2O 5, Cr 2O 3, Mn 3O 4, Co 3O 4, NiO, CuO and ZnO, respectively. The decomposition curves of the free ligand (biguanide) and biguanide sulphate are also given. The decomposition characteristics are discussed.