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Bond Order (bond + order)
Selected AbstractsBond Orders between Molecular FragmentsCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2006Adam J. Bridgeman Dr. Abstract An extension of the Mayer bond order for the interaction between molecular fragments is presented. This approach allows the classical chemical concepts of bond order and valence to be utilised for fragments and the interactions between the fragments and symmetry-adapted linear combinations to be analysed. For high-symmetry systems, the approach allows the contribution from each irreducible representation to be assessed and provides a semiquantitative measure of the role of each bonding mode to interfragment interactions. The utility of this tool has been examined by a study of the bonding in symmetrical sandwich complexes. The validity of the frontier-orbital approach and the contributions from each frontier-orbital interaction can also be assessed within this model. As demonstrated by a study of a number of mixed-sandwich complexes, the model proves to be especially useful for low-symmetry systems in which separation of the ,, , and , roles in bonding of the ligand is difficult to assess. The fragment bond order describes the interaction between preoptimized fragment orbitals and is independent of the charges that are placed on these fragments. Although the method allows the chemist to define fragments in any way they choose, most insight is gained by using the same frontier orbitals employed so successfully in perturbational molecular-orbital approaches. The results are free from the influence of the electron-counting method used to describe fragments, such as the rings and metals in sandwich complexes. [source] Comment on "Disproving a Silicon Analog of an Alkyne with the Aid of Topological Analyses of the Electronic Structure and Ab Initio Molecular Dynamics Calculations"CHEMPHYSCHEM, Issue 4 2006Gernot Frenking Prof. Dr. Bond order of a silicon-silicon bond (1): The statement that the recently synthesized compound RSiSiR (1) (RSi[C(SiMe3)3]2CHMe2) has rather a double than a triple bond is challenged. Arguments are given which support the interpretation of the bonding situation in terms of two donor,acceptor bonds which are enhanced by one , bond (see picture). [source] Electronic Structure of Linearly Coordinated EQ Complexes of the Type [(N3N)W(EQ)] [N3N = N(CH2CH2NSiMe3)3; E = P, As, Sb, Bi; Q = O, S, Se, Te]: A DFT StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2007Gábor Balázs Abstract Density functional theory (DFT) calculations were carried out on the terminal EQ complexes [(N3N)W(EQ)] {N3N = N(CH2CH2NSiMe3)3; E = P, As, Sb, Bi; Q = O, S, Se Te} to clarify the bonding situation within the linear Nax,W,E,Q core. This unusual structural motif gives rise to a bonding arrangement in which the ,-electron density is delocalised over the three atoms of the W,E,Q unit. Fragment calculations and natural bond order (NBO) data indicated that the ,-bonding component of the Nax,W,E,Q unit comprises two occupied , orbitals, while the , component of bonding comprises two sets of degenerate , orbitals. In general, the , orbitals of the Nax,W,E,Q core are higher in energy compared to the , orbitals. The phosphorus monoxide (EQ = PO) complexes provide an exception to this rule, with the 1, orbitals of the W,P,O core lower in energy than the , orbitals. Generally, as the atomic number of either the pnicogen (E) or chalcogen (Q) atom increases the extent of ,-orbital delocalisation decreases, whereas the ,-orbital delocalisation increases. Fractional bond orders and Wiberg bond indices were used to establish whether localisation of the ,-electron density gives rise to a W,E or an E,Q double or triple bond. Both methods indicate a W,E as well as an E,Q double bond. The ionic nature of the complexes were analysed by inspection of the Hirschfeld charge distribution which shows only a moderate ionic character. Exceptions are the pnicogen monoxide complexes, which are more ionic. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] 33S NMR shieldings and chemical bonding in compounds of sulfurHETEROATOM CHEMISTRY, Issue 3 2004D. B. Chesnut Sulfur nuclear magnetic resonance (NMR) chemical shieldings have been determined at the correlation-including density functional theory scaled B3LYP/6-311+G(nd,p)//B3LYP/6-311+G(d,p) and modified MP2/6-311+G(nd,p) estimated infinite order Mřller-Plesset levels with n = 2 for sulfur. The calculations span the range of sulfur shieldings and show agreement with experiment of about 3% of the shielding range. The atoms-in-molecules delocalization index and a covalent bond order from specific localized orbitals in the DFT approach are used to characterize sulfur's bonding and to relate it, where possible, to the calculated shieldings. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:216,224, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20000 [source] The charge capacitance of the chemical bond: Application to bonds containing metalsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2009Asbjřrn Holt Abstract The charge capacitance of metal containing complexes are studied. For molecules with multiple bonding between the metal atoms it is found that the charge capacitance is correlated to the maximum bond order, natural bond order, and to some extent the effective bond order. Furthermore the charge capacitance of some methylidene metal dihydride complexes are studied. These molecules have agostic interactions of varying strength, and it is concluded that this strength is very well reflected in the charge capacitances of the systems. In accordance with the definition of agostic interactions it is therefor concluded that the charge capacitance holds information about the strength of covalent interactions. The effect therefore on the agostic interactions upon substitution of one of the hydrogen atoms with fluorine in the methylidene metal complexes is studied, and found to reduce the agostic interactions. It is also demonstrated that there is an agostic interaction in an ArCrCrAr complex. The distance dependence of the charge capacitance is also discussed. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Quasi-classical dynamical properties and reaction rate of the Na + HF system on two different potential energy surfacesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2005Alessandra F. A. Vilela Abstract Detailed dynamical properties and reaction rate calculations for the ground-state Na + HF , NaF + H reaction are carried out using two different potential energy surfaces (PES): generalized simulated annealing PES (GSA PES) and bond order 5 PES (BO5 PES). These studies show that the quality and efficacy of the GSA PES are comparable to the best PES (BO5 PES) found in the literature. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Bond length features of linear carbon chains of finite to infinite size: Visual interpretation from Pauling bond ordersINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2003Zexing Cao Abstract Schemes for Kekulé structure counting of linear carbon chains are suggested. Mathematical formulas, which calculate the Pauling bond order P(k, N) of a chemical bond numbered by k, are given for the carbon chain with N carbon atoms. By use of the least-squares fitting of a linearity, relationships between Pauling bond orders and bond lengths are obtained, and such correlation of the Pauling bond order,bond length can be qualitatively extended to the excited states. The relative magnitudes of Pauling bond orders in unsaturated carbon chains dominate C,C bond lengths a well as the bond length feature with the chain size increasing. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 144,149, 2003 [source] Advancing beyond charge analysis using the electronic localization function: Chemically intuitive distribution of electrostatic momentsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2008Julien Pilmé Abstract We propose here an evaluation of chemically intuitive distributed electrostatic moments using the topological analysis of the electron localization function (ELF). As this partition of the total charge density provides an accurate representation of the molecular dipole, the distributed electrostatic moments based on the ELF partition (DEMEP) allows computing of local moments located at non atomic centers such as lone pairs, , bonds and , systems. As the local dipole contribution can be decomposed in polarization and charge transfer components, our results indicate that local dipolar polarization of the lone pairs and chemical reactivity are closely related whereas the charge transfer contribution is the key factor driving the local bond dipole. Results on relevant molecules show that local dipole contributions can be used to rationalize inductive polarization effects in alcohols derivatives and typical hydrogen bond interactions. Moreover, bond quadrupole polarization moments being related to a , character enable to discuss bond multiplicities, and to sort families of molecules according to their bond order. That way, the nature of the CO bond has been revisited for several typical systems by means of the DEMEP analysis which appears also helpful to discuss aromaticity. Special attention has been given to the carbon monoxide molecule, to the CuCO complex and to a weak intramolecular N|---CO interaction involved in several biological systems. In this latter case, it is confirmed that the bond formation is mainly linked to the CO bond polarization. Transferability tests show that the approach is suitable for the design of advanced force fields. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008 [source] Experimental and theoretical studies of the elimination kinetics of 3-hydroxy-3-methyl-2-butanone in the gas phaseJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 7 2005Mariana Graterol Abstract The kinetics of the gas-phase elimination of 3-hydroxy-3-methyl-2-butanone was investigated in a static system, seasoned with allyl bromide, and in the presence of the free chain radical inhibitor toluene. The working temperature and pressure range were 439.6,489.3°C and 81,201.5,Torr (1,Torr,=,133.3,Pa), respectively. The reaction was found to be homogeneous, unimolecular and to follow a first-order rate law. The products of elimination are acetone and acetaldehyde. The temperature dependence of the rate coefficients is expressed by the following equation: log[k1(s,1)],=,(13.05±0.53),(229.7±5.3),kJ,mol,1 (2.303RT),1. Theoretical estimations of the mechanism of this elimination suggest a molecular mechanism of a concerted non-synchronous four-membered cyclic transition-state process. An analysis of bond order and natural bond orbital charges suggests that the bond polarization of C(OH),C(O),, in the sense of C(OH),+&·C(O),,, is rate limiting in the elimination reaction. The rate coefficients obtained experimentally are in reasonably good agreement with the theoretical calculations. The mechanism of 3-hydroxy-3-methyl-2-butanone elimination is described. Copyright © 2005 John Wiley & Sons, Ltd. [source] Structural characterization of p -benzosemiquinone radical in a solid state: the radical stabilization by a low-barrier hydrogen bondACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2006imir Mol Semiquinone (p -benzosemiquinone), a transient organic radical, was detected in the solid state by EPR spectroscopy revealing four symmetrically equivalent protons. A variable-temperature X-ray diffraction analysis (293 and 90,K) and EPR data support a dynamical disorder of the proton. A low-barrier O,H···O hydrogen bond stabilizes the radical. The C,O bond length is 1.297,(4),Ĺ, corresponding to a bond order of ca 1.5. The geometry of the radical implies an electron delocalization throughout the benzenoid ring. Two polymorphs of semiquinone, monoclinic and triclinic, were observed and their structures determined. Their crystal packings were compared with those of quinhydrone polymorphs. [source] Bond Orders between Molecular FragmentsCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2006Adam J. Bridgeman Dr. Abstract An extension of the Mayer bond order for the interaction between molecular fragments is presented. This approach allows the classical chemical concepts of bond order and valence to be utilised for fragments and the interactions between the fragments and symmetry-adapted linear combinations to be analysed. For high-symmetry systems, the approach allows the contribution from each irreducible representation to be assessed and provides a semiquantitative measure of the role of each bonding mode to interfragment interactions. The utility of this tool has been examined by a study of the bonding in symmetrical sandwich complexes. The validity of the frontier-orbital approach and the contributions from each frontier-orbital interaction can also be assessed within this model. As demonstrated by a study of a number of mixed-sandwich complexes, the model proves to be especially useful for low-symmetry systems in which separation of the ,, , and , roles in bonding of the ligand is difficult to assess. The fragment bond order describes the interaction between preoptimized fragment orbitals and is independent of the charges that are placed on these fragments. Although the method allows the chemist to define fragments in any way they choose, most insight is gained by using the same frontier orbitals employed so successfully in perturbational molecular-orbital approaches. The results are free from the influence of the electron-counting method used to describe fragments, such as the rings and metals in sandwich complexes. [source] Disproving a Silicon Analog of an Alkyne with the Aid of Topological Analyses of the Electronic Structure and Ab Initio Molecular Dynamics CalculationsCHEMPHYSCHEM, Issue 9 2005Carlo A. Pignedoli Dr. Abstract A silicon compound has recently been synthesized that was claimed to exhibit the first realization of a silicon,silicon triple bond. We debate this classification on the basis of a thorough investigation of the nature of the chemical bond, using the rigorous topological analysis of the electron density as developed in Bader's atoms-in-molecules theory, that of the electron localization function and the related orbital-independent definitions of the bond order. Our results refer both to the ground-state geometry and to nonequilibrium configurations, which are accessed by the system in a room-temperature ab initio molecular dynamics simulation. We also use the reciprocal compliance force constant as an independent chemical descriptor. All the above procedures are in agreement and do not support the classification of the silicon,silicon central bond as triple. The characterization which consistently emerges from the present study is one in which two electron pairs participate in the bonding and the other pair belongs mainly to nonbonding regions. [source] Theoretical Investigation on the Mechanism and Design of Catalysts for Nitrolysis of Hexamine,CHINESE JOURNAL OF CHEMISTRY, Issue 9 2010Liangwei Shi Abstract The mechanism of nitrolysis of hexamine (HA) by DFT method has been explored to understand the classical organic reaction and assist the design of new catalyst. The potential energy surface of NO+2 was firstly investigated. A reasonable configuration evolution of NO+2 during the process of its reaction with HA was figured out. The role of H+ and NH+4 for the nitrolysis of HA was analyzed and discussed. The route of nitrolysis reaction from HA to 1-acetoxylmethene-3-nitro-tetrazabicyclo[3,3,1]nonane intermediate is similar to that of acetylation of HA. The relative free energy calculation proves the priority of nitrolysis relative to acetylation. Two types of Lewis salts, M(OSO2CF3)3 and M[N(SO2CF3)2]3 (M: Yb, Sm, Y, and Eu), are designed on the basis of discussed mechanism. The calculation for the key bond order in IM2[CH2R] model intermediates gives an indicator as the preferable catalyst. The experimental results support the theoretical conclusion. [source] Vanadium Carbonyl Nitrosyl Compounds: The Carbonyl Nitrosyl Chemistry of an Oxophilic Early Transition MetalEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2009Hongyan Wang Abstract The vanadium carbonyl nitrosyl compounds V(NO)(CO)n (n = 5, 4, 3) and V2(NO)2(CO)n (n = 9, 8, 7) have been examined by density functional theory in order to assess the effect of the oxophilicity of vanadium on its metal carbonyl nitrosyl chemistry. The expected octahedral structure for the experimentally known, but surprisingly unstable, V(NO)(CO)5, is confirmed by DFT. The optimized structures of the unsaturated derivatives V(NO)(CO)4 and V(NO)(CO)3 can be derived from the octahedral V(NO)(CO)5 structure by loss of one or two carbonyl groups, respectively. This leads to anearly square-planar predicted structure for V(NO)(CO)3. The lowest energy structures for the binuclear derivatives V2(NO)2(CO)n (n = 9, 8, 7) have exclusively two-electron donor carbonyl groups and three-electron donor linear nitrosyl groups with metal,metal distances corresponding to the formal bond orders required for the favored 18-electron configurations. Bridging carbonyl groups appear to be preferred energetically over bridging nitrosyl groups in the V2(NO)2(CO)n structures in contrast to the similar carbonyl nitrosyl compounds of later transition metals. The saturated V2(NO)2(CO)9, with a relatively long V,V distance of 3.583 Ĺ (B3LYP) or 3.205 Ĺ (BP86), is thermodynamically unstable with respect to dissociation into V(NO)(CO)5 + V(NO)(CO)4.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Electronic Structure of Linearly Coordinated EQ Complexes of the Type [(N3N)W(EQ)] [N3N = N(CH2CH2NSiMe3)3; E = P, As, Sb, Bi; Q = O, S, Se, Te]: A DFT StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2007Gábor Balázs Abstract Density functional theory (DFT) calculations were carried out on the terminal EQ complexes [(N3N)W(EQ)] {N3N = N(CH2CH2NSiMe3)3; E = P, As, Sb, Bi; Q = O, S, Se Te} to clarify the bonding situation within the linear Nax,W,E,Q core. This unusual structural motif gives rise to a bonding arrangement in which the ,-electron density is delocalised over the three atoms of the W,E,Q unit. Fragment calculations and natural bond order (NBO) data indicated that the ,-bonding component of the Nax,W,E,Q unit comprises two occupied , orbitals, while the , component of bonding comprises two sets of degenerate , orbitals. In general, the , orbitals of the Nax,W,E,Q core are higher in energy compared to the , orbitals. The phosphorus monoxide (EQ = PO) complexes provide an exception to this rule, with the 1, orbitals of the W,P,O core lower in energy than the , orbitals. Generally, as the atomic number of either the pnicogen (E) or chalcogen (Q) atom increases the extent of ,-orbital delocalisation decreases, whereas the ,-orbital delocalisation increases. Fractional bond orders and Wiberg bond indices were used to establish whether localisation of the ,-electron density gives rise to a W,E or an E,Q double or triple bond. Both methods indicate a W,E as well as an E,Q double bond. The ionic nature of the complexes were analysed by inspection of the Hirschfeld charge distribution which shows only a moderate ionic character. Exceptions are the pnicogen monoxide complexes, which are more ionic. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Atomic-orbital-symmetry based ,-, ,-, and ,-decomposition analysis of bond ordersINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 11 2009Olga V. Sizova Abstract The atomic-orbital-symmetry based (AOSB) scheme for the decomposition of Mayer and Wiberg bond orders into ,-, ,-, and ,-components is used to investigate different types of covalent bonds. Four series of compounds are studied: simple molecules with homonuclear bonds, inorganic molecules with polar heteronuclear bonds, [Ru(CN)5(XY)]q transition metal complexes with ,-acceptor ligands, and dimetal complexes with multiple metal,metal bonds. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Semiempirical electronic structure calculation on Ca and Pb apatitesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4 2009Maria Matos Abstract A systematic study is made on the electronic structure of stoichiometric calcium and lead apatites, using the tight binding extended Hückel method (eHT). The aim is to investigate the applicability of the semiempirical theory to study this family of compounds. A10(BO4)6X2 (A = Ca, Pb) apatites, differing by substitutions in the BO4 tetrahedral unit (B = P, As, and V) and X-channel ion (X = OH, Cl), are considered. The calculations show that eHT is suitable to describe basic properties especially concerning trends with atomic substitution and geometry changes. Band structure, Mulliken charge distribution, and bond orders are in good agreement with results of ab initio density functional theory (DFT) found in the literature. Large variations in the optical gap due to vanadium and lead substitutions are newly found. Changes in the anion X-channel affect the optical gap, which is in close agreement with DFT results. Analysis involving subnets are performed to determine the role of halogenic orbitals in the electronic structure of chloroapatites, showing evidence of covalent Cl bonding. It was also found that PbOH bonding in hydroxy-vanadinite Pb10(VO4)6(OH)2, recently synthesized, is weaker than that of CaOH in vanadate Ca10(VO4)6(OH)2. Arsenium is found to be more weakely bound to the O-tetrahedron than phosphorous, although CaO bond is increased with the substitution. We investigate, in addition, the electronic structure of a model system Ca10(AsO4)6(OH)2, obtained from direct As substitution in the vanadate Ca10(VO4)6(OH)2. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Theoretical study of the gas-phase SN2 reactions of X, with CH3OY (X, Y = Cl, Br, I)INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2007Jing-Gang Gai Abstract The gas-phase nucleophilic substitution reactions at saturated oxygen X, + CH3OY (X, Y = Cl, Br, I) have been investigated at the level of CCSD(T)/6-311+G(2df,p)//B3LYP/6-311+G(2df,p). The calculated results indicate that X, preferably attacks oxygen atom of CH3OY via a SN2 pathway. The central barriers and overall barriers are respectively in good agreement with both the predictions of Marcus equation and its modification, respectively. Central barrier heights (,H and ,H) correlate well with the charges (Q) of the leaving groups (Y), Wiberg bond orders (BO) and the elongation of the bonds (OY and OX) in the transition structures. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Electronic structure and physicochemical properties of selected penicillinsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2007Catalina Soriano-Correa Abstract Traditionally, penicillins have been used as antibacterial agents due to their characteristics and widespread applications with few collateral effects, which have motivated several theoretical and experimental studies. Despite the latter, their mechanism of biological action has not been completely elucidated. We present a theoretical study at the Hartree,Fock and density functional theory (DFT) levels of theory of a selected group of penicillins such as the penicillin-G, amoxicillin, ampicillin, dicloxacillin, and carbenicillin molecules, to systematically determine the electron structure of full ,-lactam antibiotics. Our results allow us to analyze the electronic properties of the pharmacophore group, the aminoacyl side-chain, and the influence of the substituents (R and X) attached to the aminoacyl side-chain at 6, (in contrast with previous studies focused at the 3, substituents), and to corroborate the results of previous studies performed at the semiempirical level, solely on the ,-lactam ring of penicillins. Besides, several density descriptors are determined with the purpose of analyzing their link to the antibacterial activity of these penicillin compounds. Our results for the atomic charges (fitted to the electrostatic potential), the bond orders, and several global reactivity descriptors, such as the dipole moments, ionization potential, hardness, and the electrophilicity index, led us to characterize: the active sites, the effect of the electron-attracting substituent properties and their physicochemical features, which altogether, might be important to understand the biological activity of these type of molecules. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Ab initio calculations and analysis of chemical bonding in SrTiO3 and SrZrO3 cubic crystalsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2006R. A. Evarestov Abstract The possibility of the different first-principles methods to describe the chemical bonding in SrTiO3 and SrZrO3 cubic crystals is investigated. The local properties of the electronic structure (atomic charges, bond orders, atomic delocalization indexes, and polarization fractions) were calculated with different methods: traditional Mulliken population analysis in LCAO calculations, two projection techniques in plane-wave (PW) calculations, population analysis based on Wannier-type atomic orbitals, and chemical bonding analysis based on the localized Wannier functions for occupied (valence band) LCAO states. All the techniques considered except the traditional Mulliken analysis demonstrate that the ionicity of chemical bonding in SrZrO3 is larger than in SrTiO3, in agreement with the Zr and Ti electronegativities relation and the relative bandgaps observed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Bond length features of linear carbon chains of finite to infinite size: Visual interpretation from Pauling bond ordersINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2003Zexing Cao Abstract Schemes for Kekulé structure counting of linear carbon chains are suggested. Mathematical formulas, which calculate the Pauling bond order P(k, N) of a chemical bond numbered by k, are given for the carbon chain with N carbon atoms. By use of the least-squares fitting of a linearity, relationships between Pauling bond orders and bond lengths are obtained, and such correlation of the Pauling bond order,bond length can be qualitatively extended to the excited states. The relative magnitudes of Pauling bond orders in unsaturated carbon chains dominate C,C bond lengths a well as the bond length feature with the chain size increasing. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 144,149, 2003 [source] Nucleation of Hydroxyapatite Crystal through Chemical Interaction with CollagenJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000Sang-Hoon Rhee The nucleation of hydroxyapatite (HAp) crystal through chemical interaction with collagen was investigated. A collagen membrane was soaked in a supersaturated simulated body fluid (1.5 SBF) solution with ion concentrations at 1.5 times that of normal simulated body fluid (1.0 SBF). A few carbonate-containing HAp crystals were formed mostly on the edge-side of the collagen membrane after 4 weeks. In the Fourier-transform infrared spectometry (FTIR) results, the carboxylate band of the collagen membrane showed red chemical shifts after the formation of HAp crystals, which coincided well with the decrease of the calculated bond orders of the carboxylate group when chelated with a calcium ion, which emulated the first-step nucleation of HAp crystal on the carboxylate group of collagen. The result implies that the binding of a calcium ion to the carboxylate group of collagen is one of the key factors for the nucleation of HAp crystals in a 1.5 SBF solution. [source] | ||||||||||||||||||||||