Simultaneous generation of H_(2) fuel and value-added chemicals has attracted increasing attention since the photogenerated electrons and holes can be both employed to convert solar light into chemical energy.Herein,f...Simultaneous generation of H_(2) fuel and value-added chemicals has attracted increasing attention since the photogenerated electrons and holes can be both employed to convert solar light into chemical energy.Herein,for realizing UV-visible-NIR light driven dehydrogenation of benzyl alcohol(BA)into benzaldehydes(BAD)and H_(2),a novel localized surface plasmon resonance(LSPR)enhanced S-scheme heterojunction was designed by combining noble-metal-free plasmon MoO_(3-x) as oxidation semiconductor and Zn_(0.1)Cd_(0.9)S as reduction semiconductor.The photoredox system of Zn_(0.1)Cd_(0.9)S/MoO_(3-x) displayed an unconventional reaction model,in which the BA served as both electron donor and acceptor.The S-scheme charge transfer mechanism induced by the formed internal electric field enhanced the redox ability of charge carriers thermodynamically and boosted charge separation kinetically.Moreover,due to the LSPR effect of MoO_(3-x) nanosheets,Zn_(0.1)Cd_(0.9)S/MoO_(3-x) photocatalysts exhibited strong absorption in the region of full solar spectrum.Therefore,the Zn_(0.1)Cd_(0.9)S/MoO_(3-x) composite generated H_(2) and BAD simultaneously via selective oxidation of BA with high production(34.38 and 33.83 mmol×g^(–1) for H_(2) and BAD,respectively)upon full solar illumination.Even under NIR light irradiation,the H_(2) production rate could up to 94.5 mmol×g^(–1)×h^(–1).In addition,the Zn_(0.1)Cd_(0.9)S/MoO_(3-x) composite displayed effective photocatalytic H_(2) evolution rate up to 149.2 mmol×g^(–1)×h^(–1) from water,which was approximate 6 times that of pure Zn_(0.1)Cd_(0.9)S.This work provides a reference for rational design of plasmonic S-scheme heterojunction photocatalysts for coproduction of high-value chemicals and solar fuel production.展开更多
We investigate the thermoelectric properties of GaN with p- and n-type doping by the first principles calculation and the semi-classical Boltzmann theory. We find that the power factors （Sacr） of p-type GaN （-3500 ...We investigate the thermoelectric properties of GaN with p- and n-type doping by the first principles calculation and the semi-classical Boltzmann theory. We find that the power factors （Sacr） of p-type GaN （-3500 μW/mK2） is about twice that of the n-type （-1750 μW/mK2）, which indicates the thermoelectric properties of p-type GaN would be better. Thermal conductivity of GaN crystal decreases rapidly as the temperature increases, but it is still too large for thermoelectric applications. The figure of merit （ZT） estimated at 1500 K is 0.134 for p-type GaN crystal and 0.062 for the n-type.展开更多
The properties of excited states and second-order nonlinear optics for supramolecule [(H2N)2+C- NH(CH2)3CH(NH3)+COO-H2PO4-H2O] from L-arginine phosphate monohydrate (LAP) crystals were calculated by using the CIS and ...The properties of excited states and second-order nonlinear optics for supramolecule [(H2N)2+C- NH(CH2)3CH(NH3)+COO-H2PO4-H2O] from L-arginine phosphate monohydrate (LAP) crystals were calculated by using the CIS and finite-field RHF methods, respectively. The results revealed that the second-order nonlinear optical (NLO) response for this crystal originates largely from the contributions of intramolecular charge transfer of arginine, and the intermolecular charge transfer between arginine and H2PO4- plays an important role as well. The conclusion can help to understand the origin of NLO response in the inorganic-organic hybrid materials.展开更多
We present a quantum-chemical analysis of the relationship between the bond length alteration （BLA） and the static first hyperpolarizability of a series of one-dimensional （1D） chromophores with donor-bridge-accep...We present a quantum-chemical analysis of the relationship between the bond length alteration （BLA） and the static first hyperpolarizability of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures. The calculated results show that the parameter BLA can be considered as an indicator to evaluate the molecular first hyper- polarizability. Along the direction of molecular ground-state dipole moments, the evolutions of BLA can be classified into three categories： the first is a non-monotonic line, which represents most chromophores; the second is monotonic increasing; and the third, contrarily, is monotonic decreasing. On the whole, the first hyperpolarizabilities of these studied chromophores are the monotonic functions of BLA along the direction of dipole moments. Therefore, the first hyperpolarizability of these 1D chromophores can be preliminarily evaluated in terms of the development of BLA without a rigorous computation. In other words, one can roughly estimate the relative magnitude of the first hyperpolarizability according to the optimized geometry.展开更多
In this paper, density functional computations have been applied to the structural, elastic and electronic properties of ternary transition metal diborides Re0.5Ir0.5B2, Re0.5Tc0.5B2, Os0.5W0.5B2 and Os0.5Ru0.5B2 in h...In this paper, density functional computations have been applied to the structural, elastic and electronic properties of ternary transition metal diborides Re0.5Ir0.5B2, Re0.5Tc0.5B2, Os0.5W0.5B2 and Os0.5Ru0.5B2 in hexagonal （P63/mmc） and orthorhombic （Pmmn） structures with both local density approximation and generalized gradient approximation. LDA gives smaller lattice parameters and larger elastic moduli than GGA. Both results show that the hexagonal ones are more stable than orthorhombic ones except Os0.5Ru0.5B2. Moreover, the hexagonal structure has superior elastic property than orthorhombic one. Generally speaking, the calculated elastic moduli of Re0.5Ir0.5B2 and Os0.5Ru0.5B2 are smaller than those values of Re0.5Tc0.5B2 and Os0.5W0.5B2 within the same structure because of the filling of antibonding states. The relativistic effects result in weaker bonds of Tc-B （Ru-B） than those of Re-B （Os-B）. All the diborides are ultra-incompressible. Re0.5Tc0.5B2 has the largest shear modulus and it is a promising superhard diboride like Os0.5W0.5B2. The elastic properties are in high correlation with the bond strength. The shear moduli are more sensitive than the bulk moduli to the bond strength.展开更多
The ground-state dipole moments and second-order nonlinear optical （NLO） properties of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures have been investigated by using ...The ground-state dipole moments and second-order nonlinear optical （NLO） properties of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures have been investigated by using the second-order MФller-Plesset （MP2） and density functional theory （DFT） methods with the basis set of 6-31＋G（d）. According to the calculated results, the relationship between the molecular static first hyperpolarizability （βμ） and the directions of electron transition has been summarized. In terms of the sign of βμ, these 1D organic chromophores were classified into two categories： type Ⅰ with negative βμ and type Ⅱ bearing positive βμ. The analyses show that the remarkable difference of the first hyperpolarizabilities between Ⅰ and Ⅱ chromophores is associated mainly with the electrostatic interaction between terminal groups and the transport electrons in excited states. Moreover, different from the popular viewpoint, the obtained results also show that most of this series of 1D D-B-A molecules are more charge-separated in the ground states than in the excited states. As a whole, this theoretical investigation, to some extent, can be considered as a useful reference in designing the NLO chromophores with large first hyperpolarizabilities.展开更多
The interaction of Cd2＋ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory（DFT） calculations.For uracil and 2,4-dithiouracil,where the two basic sites...The interaction of Cd2＋ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory（DFT） calculations.For uracil and 2,4-dithiouracil,where the two basic sites are the same,Cd2＋ attachment to the heteroatom at position 4 is preferred.However,for the systems where both types of basic centers,a carbonyl and a thiocarbonyl groups,are present,Cd2＋ association with sulfur is favorable.The enhanced stability of these enolic and thiol forms comes from Cd2＋ interaction with two basic sites simultaneously,which thereby triggers a significant aromatization of the ring.More significantly,the Cd2＋ binding energy with uracil and its thio-derivatives is larger than the tautomerization barriers connecting the diketo-like forms with the corresponding enolic-like tautomers.Consequently,when associated with Cd2＋,all tautomers are energetically accessible and should be observed in the gas phase.展开更多
Mixed-metal carbonyl clusters of W2Ir2（CO）10（η^5-C5H4Me）2 1 and W2Ir2（μ-L）（CO）8（η^5-C5H4Me）2 （L = dppe 2, dppf 3） have been studied by TDDFT method focusing on their electronic and nonlinear optical pro...Mixed-metal carbonyl clusters of W2Ir2（CO）10（η^5-C5H4Me）2 1 and W2Ir2（μ-L）（CO）8（η^5-C5H4Me）2 （L = dppe 2, dppf 3） have been studied by TDDFT method focusing on their electronic and nonlinear optical properties. These three clusters exhibit the first static hyperpolarizabilities of medium magnitude （βtot-10×10^-30 esu）. The origin of β is discussed by the new proposed orbital-pair decomposition scheme by Barandes et al. The result suggests that the β values of the two clusters are mainly originated from d-d electron transition within the metal skeleton, and d-p （π＊） electron transition from metals to carbonyls and phenyl. The additional coordination by the electron donor group, ferrocene, makes cluster 3 own much larger β values, and the relatively longer range charge transfer from d orbitals of ferrocene to d orbirals of Ir and W is responsible for the enhanced β values.展开更多
A series of tetrahedral iridium carbonyl clusters coordinated by systematically varied series of ligands have been studied by TDDFT method focusing on their electronic and non- linear optical properties. The clusters ...A series of tetrahedral iridium carbonyl clusters coordinated by systematically varied series of ligands have been studied by TDDFT method focusing on their electronic and non- linear optical properties. The clusters of Ir4（CO）12 （1）, Ir4（μ-CO）3（CO）9 （2）, Ir4（μ-L）（CO）10 （L = dppm 3, dppe 4, （Ph2P）2CHMe 5, Ph2P（CH2）3PPh2 6） and Ir4（CO）10（phen） （phen = 1,10-phen- anthroline） （7） exhibit the first static hyperpolarizabilities of medium magnitude （βtot-10×10^-30 esu）. The second order nonlinear optical response of the seven clusters increase from 0 to 23 ×10^-30 esu; the high symmetric cluster Ir4（CO）12 debases its symmetry and presents the second order nonlinear optical behavior as the coordination style of some carbonyls changes to bridge style, and then the response increases regularly with the systematical variation of the ligands. The origination of the first hyperpolarizability is discussed by the expanded orbital decomposition scheme. The results suggest the d-d electron transition from the apical iridium atom to the other three Ir atoms inside the metal skeleton, and d-πelectron transitions from metals to carbonyls are responsible for the first hyperpolarizabilities. Particularly, for cluster 7, the charge transfer from d orbitals of iridium to π＊ orbirals of phenanthroline originates the first hyperpolarizabilities.展开更多
Time dependent density functional theory (TDDFT) has been applied to calculate the electronic structure and second order nonlinear optical (NLO) properties of some organic molecules. The two dimensional (2 D) cha...Time dependent density functional theory (TDDFT) has been applied to calculate the electronic structure and second order nonlinear optical (NLO) properties of some organic molecules. The two dimensional (2 D) charge transfer characteristics of calculated molecules were studied and compared with corresponding experimental results. All the theoretical results agree well with the measurement. For 2 D molecule with two fold symmetry, the dominant charge transfer is off diagonal, while for three fold symmetry 2 D molecule, the dominant charge transfer is not only between branches and central group but also among branches.展开更多
Theoretical study was performed to investigate how the hydration of cadmium ca-tion influences the structure and properties of guanine.The aqueous environment was simulated by both explicit solvent（1-5 water molecule...Theoretical study was performed to investigate how the hydration of cadmium ca-tion influences the structure and properties of guanine.The aqueous environment was simulated by both explicit solvent（1-5 water molecules） model and implicit solvent model.For complexes in which Cd2＋ attached to the N（7） and O（6） sites of guanine,energy analysis together with the Natural Bonding Orbital（NBO） analysis were performed to elucidate the bonding characteristics in detail.The most stable structures are penta-coordinate complexes without aqua ligand located at the guanine site.Higher number of water ligands corresponds to higher stabilization energies.Average bonding energies of G-Cd increase with the number of water molecules.Bonding energies of water ligands depend on its position in the complexes.The charge distribution of guanine changed with increasing the number of water ligands,which may also influence the base-pairing pattern of guanine.There is positive charge transfer from guanine to aqua ligand as the number of the hydration waters increases.IEFPCM optimization has results comparable to the [CdG（H2O）5]2＋ structure 5a.展开更多
In the framework of density functional theory （DFT）, the electronic excitations and nonlinear optical （NLO） properties of six binuclear transition metal cluster anions with the formula of [Ch2M-（μ-Ch）2-M＇CN]^...In the framework of density functional theory （DFT）, the electronic excitations and nonlinear optical （NLO） properties of six binuclear transition metal cluster anions with the formula of [Ch2M-（μ-Ch）2-M＇CN]^2- （M = Mo, W; Ch = S, Se; M＇ = Cu, Ag） have been systemically investigated at both cases of gas phase and DMF solution. The obtained electronic absorption spectra reveal that the element replacements of metals M and ligands Ch have significant influence on the absorptions, especially on the low-lying ones. In addition, the transitions of μ-Ch→M are dominant for the low-lying excitations, whereas the transitions of M＇→M as well as Ch→M are mainly responsible for the higher excitations. The calculated molecular first and second hyperpolarizabilities present the remarkable element substitution and solvent effects. The analyses show that the transitions involving μ-Ch→M charge transfer make the critical contributions to the first hyperpolarizability t, and that the charge transfers from the moieties of MCh4 to M＇CN as well as those of μ-Ch→M and M＇→M are responsible for the second hyperpolarizability y. Moreover, the introduction of solvent leads to the results that the transitions within the moieties of MCh4 and M＇CN make larger contributions to the hyperpolarizability, especially to γ.展开更多
文摘Simultaneous generation of H_(2) fuel and value-added chemicals has attracted increasing attention since the photogenerated electrons and holes can be both employed to convert solar light into chemical energy.Herein,for realizing UV-visible-NIR light driven dehydrogenation of benzyl alcohol(BA)into benzaldehydes(BAD)and H_(2),a novel localized surface plasmon resonance(LSPR)enhanced S-scheme heterojunction was designed by combining noble-metal-free plasmon MoO_(3-x) as oxidation semiconductor and Zn_(0.1)Cd_(0.9)S as reduction semiconductor.The photoredox system of Zn_(0.1)Cd_(0.9)S/MoO_(3-x) displayed an unconventional reaction model,in which the BA served as both electron donor and acceptor.The S-scheme charge transfer mechanism induced by the formed internal electric field enhanced the redox ability of charge carriers thermodynamically and boosted charge separation kinetically.Moreover,due to the LSPR effect of MoO_(3-x) nanosheets,Zn_(0.1)Cd_(0.9)S/MoO_(3-x) photocatalysts exhibited strong absorption in the region of full solar spectrum.Therefore,the Zn_(0.1)Cd_(0.9)S/MoO_(3-x) composite generated H_(2) and BAD simultaneously via selective oxidation of BA with high production(34.38 and 33.83 mmol×g^(–1) for H_(2) and BAD,respectively)upon full solar illumination.Even under NIR light irradiation,the H_(2) production rate could up to 94.5 mmol×g^(–1)×h^(–1).In addition,the Zn_(0.1)Cd_(0.9)S/MoO_(3-x) composite displayed effective photocatalytic H_(2) evolution rate up to 149.2 mmol×g^(–1)×h^(–1) from water,which was approximate 6 times that of pure Zn_(0.1)Cd_(0.9)S.This work provides a reference for rational design of plasmonic S-scheme heterojunction photocatalysts for coproduction of high-value chemicals and solar fuel production.
基金supported by the National Natural Science Foundation of China(Nos.91122015 and 20973174)
文摘We investigate the thermoelectric properties of GaN with p- and n-type doping by the first principles calculation and the semi-classical Boltzmann theory. We find that the power factors （Sacr） of p-type GaN （-3500 μW/mK2） is about twice that of the n-type （-1750 μW/mK2）, which indicates the thermoelectric properties of p-type GaN would be better. Thermal conductivity of GaN crystal decreases rapidly as the temperature increases, but it is still too large for thermoelectric applications. The figure of merit （ZT） estimated at 1500 K is 0.134 for p-type GaN crystal and 0.062 for the n-type.
文摘The properties of excited states and second-order nonlinear optics for supramolecule [(H2N)2+C- NH(CH2)3CH(NH3)+COO-H2PO4-H2O] from L-arginine phosphate monohydrate (LAP) crystals were calculated by using the CIS and finite-field RHF methods, respectively. The results revealed that the second-order nonlinear optical (NLO) response for this crystal originates largely from the contributions of intramolecular charge transfer of arginine, and the intermolecular charge transfer between arginine and H2PO4- plays an important role as well. The conclusion can help to understand the origin of NLO response in the inorganic-organic hybrid materials.
基金the National Natural Science Foundation of China (20573114)the MOST projects of 2004CB720605and 2006DFA403020
文摘We present a quantum-chemical analysis of the relationship between the bond length alteration （BLA） and the static first hyperpolarizability of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures. The calculated results show that the parameter BLA can be considered as an indicator to evaluate the molecular first hyper- polarizability. Along the direction of molecular ground-state dipole moments, the evolutions of BLA can be classified into three categories： the first is a non-monotonic line, which represents most chromophores; the second is monotonic increasing; and the third, contrarily, is monotonic decreasing. On the whole, the first hyperpolarizabilities of these studied chromophores are the monotonic functions of BLA along the direction of dipole moments. Therefore, the first hyperpolarizability of these 1D chromophores can be preliminarily evaluated in terms of the development of BLA without a rigorous computation. In other words, one can roughly estimate the relative magnitude of the first hyperpolarizability according to the optimized geometry.
基金supported by the National Natural Science Foundation of China (No. 20973174)973 Project (2007CB805307)
文摘In this paper, density functional computations have been applied to the structural, elastic and electronic properties of ternary transition metal diborides Re0.5Ir0.5B2, Re0.5Tc0.5B2, Os0.5W0.5B2 and Os0.5Ru0.5B2 in hexagonal （P63/mmc） and orthorhombic （Pmmn） structures with both local density approximation and generalized gradient approximation. LDA gives smaller lattice parameters and larger elastic moduli than GGA. Both results show that the hexagonal ones are more stable than orthorhombic ones except Os0.5Ru0.5B2. Moreover, the hexagonal structure has superior elastic property than orthorhombic one. Generally speaking, the calculated elastic moduli of Re0.5Ir0.5B2 and Os0.5Ru0.5B2 are smaller than those values of Re0.5Tc0.5B2 and Os0.5W0.5B2 within the same structure because of the filling of antibonding states. The relativistic effects result in weaker bonds of Tc-B （Ru-B） than those of Re-B （Os-B）. All the diborides are ultra-incompressible. Re0.5Tc0.5B2 has the largest shear modulus and it is a promising superhard diboride like Os0.5W0.5B2. The elastic properties are in high correlation with the bond strength. The shear moduli are more sensitive than the bulk moduli to the bond strength.
基金supported by the National Natural Science Foundation of China (20573114)the MOST projects of 200CB720605 and 2006DFA403020
文摘The ground-state dipole moments and second-order nonlinear optical （NLO） properties of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures have been investigated by using the second-order MФller-Plesset （MP2） and density functional theory （DFT） methods with the basis set of 6-31＋G（d）. According to the calculated results, the relationship between the molecular static first hyperpolarizability （βμ） and the directions of electron transition has been summarized. In terms of the sign of βμ, these 1D organic chromophores were classified into two categories： type Ⅰ with negative βμ and type Ⅱ bearing positive βμ. The analyses show that the remarkable difference of the first hyperpolarizabilities between Ⅰ and Ⅱ chromophores is associated mainly with the electrostatic interaction between terminal groups and the transport electrons in excited states. Moreover, different from the popular viewpoint, the obtained results also show that most of this series of 1D D-B-A molecules are more charge-separated in the ground states than in the excited states. As a whole, this theoretical investigation, to some extent, can be considered as a useful reference in designing the NLO chromophores with large first hyperpolarizabilities.
基金supported by the NNSFC (20973174 and 91122015)the Young Scientist Fund of NSFC (81001403)the Youth Innovation Fund,Institute Key Program (SZD08003) of FJIRSM
文摘The interaction of Cd2＋ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory（DFT） calculations.For uracil and 2,4-dithiouracil,where the two basic sites are the same,Cd2＋ attachment to the heteroatom at position 4 is preferred.However,for the systems where both types of basic centers,a carbonyl and a thiocarbonyl groups,are present,Cd2＋ association with sulfur is favorable.The enhanced stability of these enolic and thiol forms comes from Cd2＋ interaction with two basic sites simultaneously,which thereby triggers a significant aromatization of the ring.More significantly,the Cd2＋ binding energy with uracil and its thio-derivatives is larger than the tautomerization barriers connecting the diketo-like forms with the corresponding enolic-like tautomers.Consequently,when associated with Cd2＋,all tautomers are energetically accessible and should be observed in the gas phase.
基金Supported by the National Natural Science Foundation of China (20573114)the MOST (2006DFA43020)Natural Science Foundation of Fujian Province (2006F3133)
文摘Mixed-metal carbonyl clusters of W2Ir2（CO）10（η^5-C5H4Me）2 1 and W2Ir2（μ-L）（CO）8（η^5-C5H4Me）2 （L = dppe 2, dppf 3） have been studied by TDDFT method focusing on their electronic and nonlinear optical properties. These three clusters exhibit the first static hyperpolarizabilities of medium magnitude （βtot-10×10^-30 esu）. The origin of β is discussed by the new proposed orbital-pair decomposition scheme by Barandes et al. The result suggests that the β values of the two clusters are mainly originated from d-d electron transition within the metal skeleton, and d-p （π＊） electron transition from metals to carbonyls and phenyl. The additional coordination by the electron donor group, ferrocene, makes cluster 3 own much larger β values, and the relatively longer range charge transfer from d orbitals of ferrocene to d orbirals of Ir and W is responsible for the enhanced β values.
基金Supported by the National Natural Science Foundation of China (20573114)the MOST (2006DFA43020)Natural Science Foundation of Fujian Province (2006F3133 and 13071062)
文摘A series of tetrahedral iridium carbonyl clusters coordinated by systematically varied series of ligands have been studied by TDDFT method focusing on their electronic and non- linear optical properties. The clusters of Ir4（CO）12 （1）, Ir4（μ-CO）3（CO）9 （2）, Ir4（μ-L）（CO）10 （L = dppm 3, dppe 4, （Ph2P）2CHMe 5, Ph2P（CH2）3PPh2 6） and Ir4（CO）10（phen） （phen = 1,10-phen- anthroline） （7） exhibit the first static hyperpolarizabilities of medium magnitude （βtot-10×10^-30 esu）. The second order nonlinear optical response of the seven clusters increase from 0 to 23 ×10^-30 esu; the high symmetric cluster Ir4（CO）12 debases its symmetry and presents the second order nonlinear optical behavior as the coordination style of some carbonyls changes to bridge style, and then the response increases regularly with the systematical variation of the ligands. The origination of the first hyperpolarizability is discussed by the expanded orbital decomposition scheme. The results suggest the d-d electron transition from the apical iridium atom to the other three Ir atoms inside the metal skeleton, and d-πelectron transitions from metals to carbonyls are responsible for the first hyperpolarizabilities. Particularly, for cluster 7, the charge transfer from d orbitals of iridium to π＊ orbirals of phenanthroline originates the first hyperpolarizabilities.
文摘Time dependent density functional theory (TDDFT) has been applied to calculate the electronic structure and second order nonlinear optical (NLO) properties of some organic molecules. The two dimensional (2 D) charge transfer characteristics of calculated molecules were studied and compared with corresponding experimental results. All the theoretical results agree well with the measurement. For 2 D molecule with two fold symmetry, the dominant charge transfer is off diagonal, while for three fold symmetry 2 D molecule, the dominant charge transfer is not only between branches and central group but also among branches.
基金supported by the NNSFC (20973174)the Young Scientist Fund of NSFC (81001403)+1 种基金the Youth Innovation Fundthe Institute Key Program (SZD08003) of FJIRSM
文摘Theoretical study was performed to investigate how the hydration of cadmium ca-tion influences the structure and properties of guanine.The aqueous environment was simulated by both explicit solvent（1-5 water molecules） model and implicit solvent model.For complexes in which Cd2＋ attached to the N（7） and O（6） sites of guanine,energy analysis together with the Natural Bonding Orbital（NBO） analysis were performed to elucidate the bonding characteristics in detail.The most stable structures are penta-coordinate complexes without aqua ligand located at the guanine site.Higher number of water ligands corresponds to higher stabilization energies.Average bonding energies of G-Cd increase with the number of water molecules.Bonding energies of water ligands depend on its position in the complexes.The charge distribution of guanine changed with increasing the number of water ligands,which may also influence the base-pairing pattern of guanine.There is positive charge transfer from guanine to aqua ligand as the number of the hydration waters increases.IEFPCM optimization has results comparable to the [CdG（H2O）5]2＋ structure 5a.
基金the National Natural Science Foundation of China (No. 20573114)Foundation of Fujian Province (No. 2006F3133)
文摘In the framework of density functional theory （DFT）, the electronic excitations and nonlinear optical （NLO） properties of six binuclear transition metal cluster anions with the formula of [Ch2M-（μ-Ch）2-M＇CN]^2- （M = Mo, W; Ch = S, Se; M＇ = Cu, Ag） have been systemically investigated at both cases of gas phase and DMF solution. The obtained electronic absorption spectra reveal that the element replacements of metals M and ligands Ch have significant influence on the absorptions, especially on the low-lying ones. In addition, the transitions of μ-Ch→M are dominant for the low-lying excitations, whereas the transitions of M＇→M as well as Ch→M are mainly responsible for the higher excitations. The calculated molecular first and second hyperpolarizabilities present the remarkable element substitution and solvent effects. The analyses show that the transitions involving μ-Ch→M charge transfer make the critical contributions to the first hyperpolarizability t, and that the charge transfers from the moieties of MCh4 to M＇CN as well as those of μ-Ch→M and M＇→M are responsible for the second hyperpolarizability y. Moreover, the introduction of solvent leads to the results that the transitions within the moieties of MCh4 and M＇CN make larger contributions to the hyperpolarizability, especially to γ.
