Theoretical studies of the electronic properties of three confined aromatic molecules—benzene, naphthalene and anthracene—have been presented in support of the electronic confinement effect. The confined space of the cavities has been modeled using a mica sheet with the molecule–surface distance in the range of 1.5–4.0 A. Evidence of the confinement has been revealed by semiempirical calculations, which are theoretically interpreted by means of the Huckel molecular orbital theory. It has been found that the HOMO has been predicted to be more sensitive to the confinement than the LUMO and the overall effect is a reduction on the band gap of the frontier molecular orbitals when the molecule–surface distance is less than ca. 2.5 A. The variations of the frontier orbital energies and band gaps are correlated with the increase of both Coulomb integral, α, and resonance integral, β. The order of magnitude of the energy increment of Δα and Δβ values is evaluated from data of the above semiempirical calculations. It is also found that the confinement effect is associated with the conjugated system of the aromatic molecules. The theoretical evaluations here prove that confining organic molecules in the cavities is sufficient to alter their electronic properties as a consequence of changes in the molecular orbital energies and band gaps.
{"title":"Theoretical studies of the electronic properties of confined aromatic molecules in support of electronic confinement effect","authors":"Lei Z. Zhang, P. Cheng","doi":"10.1039/B307440D","DOIUrl":"https://doi.org/10.1039/B307440D","url":null,"abstract":"Theoretical studies of the electronic properties of three confined aromatic molecules—benzene, naphthalene and anthracene—have been presented in support of the electronic confinement effect. The confined space of the cavities has been modeled using a mica sheet with the molecule–surface distance in the range of 1.5–4.0 A. Evidence of the confinement has been revealed by semiempirical calculations, which are theoretically interpreted by means of the Huckel molecular orbital theory. It has been found that the HOMO has been predicted to be more sensitive to the confinement than the LUMO and the overall effect is a reduction on the band gap of the frontier molecular orbitals when the molecule–surface distance is less than ca. 2.5 A. The variations of the frontier orbital energies and band gaps are correlated with the increase of both Coulomb integral, α, and resonance integral, β. The order of magnitude of the energy increment of Δα and Δβ values is evaluated from data of the above semiempirical calculations. It is also found that the confinement effect is associated with the conjugated system of the aromatic molecules. The theoretical evaluations here prove that confining organic molecules in the cavities is sufficient to alter their electronic properties as a consequence of changes in the molecular orbital energies and band gaps.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"54 1","pages":"62-66"},"PeriodicalIF":0.0,"publicationDate":"2003-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81922638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The second-order polarizabilities and the UV-vis-IR spectra of a transition-metal complex Co(NH3)2(L-ala–gly–gly) have been studied by using the MP2 and TDHF methods. The complex has a maximum β component in the direction from the N(alanyl) group to the N(glycyl) groups. A transparent optical spectrum region from 0.55 to 5.5 µm was found, which offers potential applications as an optical material. The alkyl substitution of the glycyl group only slightly affected the β value and retained the IR transparent region but may cause the molecules to have a favorite packing fashion in the bulk crystal that leads to larger second-order nonlinear optical coefficients.
{"title":"Theoretical studies on hyperpolarizabilities and UV-vis-IR spectra of a diamminecobalt(III) tetripeptide transition-metal complex","authors":"Chensheng Lin, Kechen Wu, Ming-Xi Zhang, C. Mang","doi":"10.1039/B307832A","DOIUrl":"https://doi.org/10.1039/B307832A","url":null,"abstract":"The second-order polarizabilities and the UV-vis-IR spectra of a transition-metal complex Co(NH3)2(L-ala–gly–gly) have been studied by using the MP2 and TDHF methods. The complex has a maximum β component in the direction from the N(alanyl) group to the N(glycyl) groups. A transparent optical spectrum region from 0.55 to 5.5 µm was found, which offers potential applications as an optical material. The alkyl substitution of the glycyl group only slightly affected the β value and retained the IR transparent region but may cause the molecules to have a favorite packing fashion in the bulk crystal that leads to larger second-order nonlinear optical coefficients.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"54 1","pages":"59-61"},"PeriodicalIF":0.0,"publicationDate":"2003-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90880129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The intermolecular free-length is evaluated by making use of thermoacoustical parameters followed by a comparative study. To achieve this objective, thermoacoustical parameters of four ternary and two quaternary liquid mixtures have been computed. These parameters have been utilized to calculate the available volume (Va), which in turn has been used to compute intermolecular free-length (Lf) for the systems under investigation. The computed values of Lf have then been compared with the values estimated from well-established thermodynamic and ultrasonic methods. To the best of our knowledge, this investigation is a pioneering attempt in evaluation of intermolecular free-length involving multicomponent liquid mixtures by making use of thermoacoustical parameters.
{"title":"Thermoacoustical approach to the intermolecular free-length of liquid mixtures","authors":"J. D. Pandey, R. Dey, J. Chhabra","doi":"10.1039/B307435H","DOIUrl":"https://doi.org/10.1039/B307435H","url":null,"abstract":"The intermolecular free-length is evaluated by making use of thermoacoustical parameters followed by a comparative study. To achieve this objective, thermoacoustical parameters of four ternary and two quaternary liquid mixtures have been computed. These parameters have been utilized to calculate the available volume (Va), which in turn has been used to compute intermolecular free-length (Lf) for the systems under investigation. The computed values of Lf have then been compared with the values estimated from well-established thermodynamic and ultrasonic methods. To the best of our knowledge, this investigation is a pioneering attempt in evaluation of intermolecular free-length involving multicomponent liquid mixtures by making use of thermoacoustical parameters.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"2015 1","pages":"55-58"},"PeriodicalIF":0.0,"publicationDate":"2003-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86104080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effect of nH2O (n = 1–3) on the association energies of H2O complexes and on the barriers for the formation of O3 in the self-reaction of HO2 reaction has been investigated by ab initio molecular orbital calculations at the modified Gaussian-2 (G2M) level of theory. The results show that H2O can affect the complex and O3 formation processes: the more H2O molecules participating in the reaction, the higher stability of the association complexes and the greater the lowering of the O3 elimination barrier becomes. For the isomers of the reactions, more hydrogen bonds being formed in the complexes enhances their stabilities. A preliminary kinetic calculation shows that below room temperature, H2O may enhance the formation of O3 noticeably.
{"title":"H2O-catalyzed formation of O3 in the self-reaction of HO2: a computational study on the effect of nH2O (n = 1–3)","authors":"R. Zhu, M. Lin","doi":"10.1039/B304383E","DOIUrl":"https://doi.org/10.1039/B304383E","url":null,"abstract":"The effect of nH2O (n \u0000= 1–3) on the association energies of H2O complexes and on the barriers for the formation of O3 in the self-reaction of HO2 reaction has been investigated by ab initio molecular orbital calculations at the modified Gaussian-2 (G2M) level of theory. The results show that H2O can affect the complex and O3 formation processes: the more H2O molecules participating in the reaction, the higher stability of the association complexes and the greater the lowering of the O3 elimination barrier becomes. For the isomers of the reactions, more hydrogen bonds being formed in the complexes enhances their stabilities. A preliminary kinetic calculation shows that below room temperature, H2O may enhance the formation of O3 noticeably.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"64 1","pages":"51-54"},"PeriodicalIF":0.0,"publicationDate":"2003-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87061660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hou Zhufeng, Zhu Zi-zhong, Huang Mei-chun, Yang Yong
By using the ab initio norm-conserving pseudopotential method, the lithium intercalations in AlSb, GaSb and InSb have been studied. The formation energies, changes of volumes, electronic structures and charge densities of the lithium interactions in zinc blende-type antimonides LixMSb (M = Al, Ga, In) are presented. Our calculations show that during lithium insertion in MSb the lithium intercalation formation energy per lithium atom are all around 2.0 eV. The volume expansions of AlSb, GaSb and InSb due to lithium insertions are relatively large, which might imply that the limit of Li intercalation in antimonides should be small.
{"title":"Formation energies of lithium intercalations in AlSb, GaSb and InSb","authors":"Hou Zhufeng, Zhu Zi-zhong, Huang Mei-chun, Yang Yong","doi":"10.1039/B304985J","DOIUrl":"https://doi.org/10.1039/B304985J","url":null,"abstract":"By using the ab initio norm-conserving pseudopotential method, the lithium intercalations in AlSb, GaSb and InSb have been studied. The formation energies, changes of volumes, electronic structures and charge densities of the lithium interactions in zinc blende-type antimonides LixMSb (M = Al, Ga, In) are presented. Our calculations show that during lithium insertion in MSb the lithium intercalation formation energy per lithium atom are all around 2.0 eV. The volume expansions of AlSb, GaSb and InSb due to lithium insertions are relatively large, which might imply that the limit of Li intercalation in antimonides should be small.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"1 1","pages":"47-50"},"PeriodicalIF":0.0,"publicationDate":"2003-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77316347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The one-dimensional algebraic model is applied to analyze infrared spectra of n-alkane molecules. We consider CH stretching vibrations in both fundamental (v = 1) and first overtone (v = 2) energy regions. We show that a relatively small set of well-defined parameters leads to a very good agreement with observed data. Both CH2 and CH3 vibrations are accounted for. In particular, we suggest that first overtone infrared spectra can be fairly well described without adding complex anharmonic (Fermi) interactions. Their inclusion is required however to obtain a closer agreement with the available experimental spectra.
{"title":"Algebraic description of n-alkane molecules: first overtone of CH stretching modes","authors":"Tijana Marinković, S. Oss","doi":"10.1039/B304717B","DOIUrl":"https://doi.org/10.1039/B304717B","url":null,"abstract":"The one-dimensional algebraic model is applied to analyze infrared spectra of n-alkane molecules. We consider CH stretching vibrations in both fundamental (v \u0000= 1) and first overtone (v \u0000= 2) energy regions. We show that a relatively small set of well-defined parameters leads to a very good agreement with observed data. Both CH2 and CH3 vibrations are accounted for. In particular, we suggest that first overtone infrared spectra can be fairly well described without adding complex anharmonic (Fermi) interactions. Their inclusion is required however to obtain a closer agreement with the available experimental spectra.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"35 1","pages":"42-46"},"PeriodicalIF":0.0,"publicationDate":"2003-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74257523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A sodium chloride supported cobalt catalyst was found to be active in the synthesis of carbon nanotubes by a CCVD method.
研究了氯化钠负载钴催化剂在碳纳米管合成中的活性。
{"title":"“Wash and go”: sodium chloride as an easily removable catalyst support for the synthesis of carbon nanotubes","authors":"A. Szabó, D. Mehn, Z. Kónya, A. Fonseca, J. Nagy","doi":"10.1039/B305670H","DOIUrl":"https://doi.org/10.1039/B305670H","url":null,"abstract":"A sodium chloride supported cobalt catalyst was found to be active in the synthesis of carbon nanotubes by a CCVD method.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"165 1","pages":"40-41"},"PeriodicalIF":0.0,"publicationDate":"2003-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79676992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we discuss the synthesis of cadmium sulfide (CdS) quantum dots within thermally evaporated sodium bis(2-ethylhexyl)sulfosuccinate (AOT) thin films. This procedure uses electrostatic interactions to entrap positively charged cadmium ions into thin films of the anionic surfactant AOT by a simple immersion of the film in electrolyte solution. Thereafter, the composite film is treated with H2S gas/Na2S solution resulting in the in-situ formation of CdS nanoparticles in the quantum size regime. It is believed that the ability of AOT molecules in the thermally evaporated thin films to form reverse micelles is responsible for the CdS nanoparticle size control observed. Investigation of the entrapment of cadmium ions in the AOT film and subsequent quantum dot synthesis was carried out by quartz crystal microgravimetry (QCM), UV-Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) measurements.
{"title":"Synthesis of CdS nanoparticles within thermally evaporated aerosol OT thin films","authors":"S. Shankar, S. Chatterjee, M. Sastry","doi":"10.1039/B303919F","DOIUrl":"https://doi.org/10.1039/B303919F","url":null,"abstract":"In this paper, we discuss the synthesis of cadmium sulfide (CdS) quantum dots within thermally evaporated sodium bis(2-ethylhexyl)sulfosuccinate (AOT) thin films. This procedure uses electrostatic interactions to entrap positively charged cadmium ions into thin films of the anionic surfactant AOT by a simple immersion of the film in electrolyte solution. Thereafter, the composite film is treated with H2S gas/Na2S solution resulting in the in-situ formation of CdS nanoparticles in the quantum size regime. It is believed that the ability of AOT molecules in the thermally evaporated thin films to form reverse micelles is responsible for the CdS nanoparticle size control observed. Investigation of the entrapment of cadmium ions in the AOT film and subsequent quantum dot synthesis was carried out by quartz crystal microgravimetry (QCM), UV-Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) measurements.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"69 1","pages":"36-39"},"PeriodicalIF":0.0,"publicationDate":"2003-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80028195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article reports on the generation of [Mm-phenyl]− (M = Mn–Cu) complexes, which are very rare cases in chemistry. Experimental results showed that the typical cation products for the reactions of all 3d transition metal clusters (Sc–Cu) with benzene were different [Mm(C6H6)n]+ (M = Sc–Cu) species, while the typical anion products for the late 3d transition metals were [Mm–C6H5]− (M = Mn–Cu) complexes. Their formation mechanisms, which involve anion metal clusters inducing a selective benzene C–H cleavage in the gas phase, were proposed.
{"title":"Generation of [Mm-phenyl]− (M = Mn–Cu) complexes in the gas phase: Metal cluster anions inducement of a selective benzene C–H cleavage","authors":"X. Xing, Hongtao Liu, Zi-Chao Tang","doi":"10.1039/B302761A","DOIUrl":"https://doi.org/10.1039/B302761A","url":null,"abstract":"This article reports on the generation of [Mm-phenyl]− \u0000(M = Mn–Cu) complexes, which are very rare cases in chemistry. Experimental results showed that the typical cation products for the reactions of all 3d transition metal clusters (Sc–Cu) with benzene were different [Mm(C6H6)n]+ \u0000(M = Sc–Cu) species, while the typical anion products for the late 3d transition metals were [Mm–C6H5]− \u0000(M = Mn–Cu) complexes. Their formation mechanisms, which involve anion metal clusters inducing a selective benzene C–H cleavage in the gas phase, were proposed.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"170 1","pages":"32-35"},"PeriodicalIF":0.0,"publicationDate":"2003-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77932190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Fukui function fk+ and local softness sk+ are assigned as reactivity parameters for nucleophilic addition reaction in acrolein, methylacrylate, methylmethacrylate, acryloylchloride, cinnamaldehyde and cinnamoylchloride. All calculations were performed at the HF level of theory using 6-31G, 6-31G** and TZV basis sets. The condensed local softness calculated using a Lowdin population is compared with the local softness calculated from a Mulliken population. The most probable sites for nucleophilic attack on the α,β-unsaturated carbonyl compounds are determined from local reactivity descriptors: they are quite reliable to predict the reactivity relative to atomic charges.
{"title":"Reactivity of α,β-unsaturated carbonyl compounds towards nucleophilic addition reaction: a local hard–soft acid–base approach","authors":"P. Mondal, Kalyan K. Hazarika, R. Deka","doi":"10.1039/B301675G","DOIUrl":"https://doi.org/10.1039/B301675G","url":null,"abstract":"The Fukui function fk+ and local softness sk+ are assigned as reactivity parameters for nucleophilic addition reaction in acrolein, methylacrylate, methylmethacrylate, acryloylchloride, cinnamaldehyde and cinnamoylchloride. All calculations were performed at the HF level of theory using 6-31G, 6-31G** and TZV basis sets. The condensed local softness calculated using a Lowdin population is compared with the local softness calculated from a Mulliken population. The most probable sites for nucleophilic attack on the α,β-unsaturated carbonyl compounds are determined from local reactivity descriptors: they are quite reliable to predict the reactivity relative to atomic charges.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"150 1","pages":"24-27"},"PeriodicalIF":0.0,"publicationDate":"2003-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77993886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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