*J Mol Graph Model ; 89: 131-138, 2019 06.*

**| MEDLINE**| ID: mdl-30884450

##### RESUMO

The iridium(III) complexes could be excellent second-order nonlinear optical (NLO) switch materials due to various advantages including abundant valence states, the diversity of coordination forms and rich electrochemical properties. In this work, the substituent effect and the multi-state switchable response of a series of novel Ir(CËN)2ADC complexes (CËNâ¯=â¯cyclometalated ligands and ADCâ¯=â¯diaminocarbene), induced by electrochemical behavior, have been calculated by density functional theory. The results show that the introducing strong electron-withdrawing groups on ADC ligands significantly enhanced the static first hyperpolarizabilities (ßtot). Moreover, a distinct improvement of the ßtot values can be found from the neutral complexes to the corresponding redox states. By this way, the remarkable multi-state NLO switch can be achieved. Remarkably, the ßtot values of the one-electron-oxidized complex 1+ and the one-electron-reduced complex 1- are â¼5.4 and â¼12.7 times larger than the corresponding neutral complex 1, respectively. The larger ßtot values are attributed to the lower transition energy and remarkable bathochromic shift of maximal absorption wavelength, which can be further illustrated by the separate distribution of ß density. We envision that these studied iridium complexes can be seen as versatile and novel second-order NLO switching materials.

*J Mol Graph Model ; 77: 363-371, 2017 10.*

**| MEDLINE**| ID: mdl-28946068

##### RESUMO

Ru metal acetylide electron donor-acceptor complexes have important applications in the field of nonlinear optics. Herein, in this work, a series of half-sandwich ruthenium-based Cp*(dpe)Ru ([Ru*]) metal complexes with the dihydroazulene/vinylheptafulvene (DHA/VHF) have been investigated by density functional theory (DFT) calculations. The results showed that the position of the [Ru*] acetylide functionality, either para or meta on the phenylene ring to the DHA/VHF core (1c/1o and 2c/2o), and additional a p-phenylene spacer (3c/3o) had a great influence on the second-order nonlinear optical (NLO) responses. The systems 1 and 3 can significantly increased second-order NLO responses compared with system 2. It was attributed to the more obvious charge transfer along y-axis, which is from [Ru*] acetylide functionality to DHA, accompanied by a significant decrease of the transition energy according electron density difference maps and time-dependent DFT calculations. The ßvec values of the open-ring complexes were larger than the corresponding closed-ring complexes owing to the smaller HOMO-LUMO gap in the open-ring complexes. It was also because of the smaller BLA values in open-ring complexes, which had stronger π-conjugation. Especially, the change ratio of ßvec value of system 2 was the largest due to the fact that their charge transfers degree varied greatly. In addition, the frequency-dependent NLO properties of the studied complexes were evaluated at 0.0239 a.u. and 0.0340 a.u. The calculation results demonstrated that the magnitude of the frequency-dependent first hyperpolarizability increased with the increasing frequency. We believe that our present work will be beneficial for further theoretical and experimental studies on large second-order NLO responses of metal complexes.

##### Assuntos

Azulenos/química , Complexos de Coordenação/química , Teoria Quântica , Rutênio/química , Elétrons , Estrutura Molecular , Óptica e Fotônica*Phys Chem Chem Phys ; 19(3): 2322-2331, 2017 Jan 18.*

**| MEDLINE**| ID: mdl-28054686

##### RESUMO

To reveal a new structure-property relationship regarding the nonlinear optical (NLO) properties of fullerenes that are associated with gamma (Î³) density, fullerenes I (C40, C50, C60 and C70), whose heights range from 4.83 to 7.96 Å, and II (C24, C36, C48 and C72), whose widths range from 4.45 to 8.22 Å, have been the research objects. Calculation of their geometric and electronic structures, absorption spectra, and the second hyperpolarizability (Î³) and the Î³ density analysis have been performed. It is found that the electronic spatial extent and the polarizability (α) value increase linearly as the fullerenes increase by every 12 carbon atoms. Similarly, the Î³ values are also proportional to the fullerene size. It is worth noting that the relative magnitude of Î³xxxx and Î³zzzz was exactly consistent with that of the width and height of fullerenes. The analysis of Î³ density provides the essential reason for this result, that is, the magnitude of the contribution to Î³ values associated with Î³ densities is proportional to the density amplitudes multiplied by the distance between them. Larger fullerenes possess larger density amplitudes and longer distances, resulting in larger Î³ values with respect to smaller fullerenes. This work presents a new structure-property interplay between the width and height of the fullerenes and their second hyperpolarizability Î³. Moreover, the Î³ density analysis provides a new insight to explore the nature of the relationship between the structure and the NLO properties.

*J Phys Chem A ; 120(46): 9330-9340, 2016 Nov 23.*

**| MEDLINE**| ID: mdl-27934245

##### RESUMO

Zwitterionic complexes have been the subject of great interest in the past several decades due to their multifunctional application in supramolecular chemistry. Herein, a series of internally stable charge-compensated carboranylated square-planar Pt(II) zwitterionic complexes have been explored by density functional theory aim to assessing their structures, the first hyperpolarizabilities, first hyperpolarizability densities, and electronic absorption spectra. It is found that the first hyperpolarizabilities of two-dimensional (2D) structure complexes are much larger with respect to the one-dimensional complex. It is ascribed to the lower transition energy and more obvious charge transfer, which can be further illustrated by their large amplitude and separate distribution of first hyperpolarizability density. In addition, the first hyperpolarizabilities of 2D complexes can be further significantly modified by introducing electron-donating/withdrawing groups on the carborane cage. As a consequence, we believe that these 2D zwitterionic complexes can behave as novel second-order nonlinear optical chromophore with a promising future.

*J Mol Graph Model ; 67: 111-8, 2016 06.*

**| MEDLINE**| ID: mdl-27262529

##### RESUMO

Carborane has been the subject of great interest over the last decades due to its high structural, chemical, biological stability and diverse applications. In the present work, carboranyl-substituted indole/indoline compounds and their functionalized derivatives have been systematically investigated by density functional theory (DFT) method with the view of assessing their electronic structures and first hyperpolarizabilities. Significantly, the first hyperpolarizabilities can be obviously enhanced by the introduction of a strong electron-withdrawing group for closed-ring forms, while the strong electron-donating group is beneficial for large first hyperpolarizabilities for open-ring forms. It indicates that the NLO properties of these compounds can be enhanced by controlling their relative substituent groups. Furthermore, the time-dependent DFT calculation illustrates that the enhancement of the first hyperpolarizabilities are found due to the obvious charge transfer (CT) transition, and closed-ring forms have a significant difference on the CT patterns versus open-ring ones. Investigation of the structure-property relationship and substituent effects at the molecular level can benefit for further exploration of carboranyl-substituted indole/indoline derivatives with versatile and fascinating NLO properties.

##### Assuntos

Compostos de Boro/química , Indóis/química , Dinâmica não Linear , Fenômenos Ópticos , Modelos Moleculares , Teoria Quântica , Eletricidade Estática , Fatores de Tempo*J Mol Graph Model ; 64: 139-146, 2016 Mar.*

**| MEDLINE**| ID: mdl-26851864

##### RESUMO

Ion-buckybowl complexes have received considerable attention in modern chemical research due to its fundamental and practical importance. Herein, we performed density functional theory (DFT) to calculate the geometical structure, binding interactions, dipole moments and the first hyperpolarizabilities (ßtot) of ion-buckybowl complexes (ions are Cl(-) and Na(+), buckybowls are quadrannulene, corannulene and sumanene). It is found that the stabilities of ion-buckybowl compounds primarily originate from the interaction energy, which was proved by a new isomerization energy decomposition analysis approach. Plots of reduced density gradient mirror the ion-π weak interaction has been formed between the ions and buckybowls. Significantly, the buckybowl subunits cannot effectively impact the nonlinear optical (NLO), but the kind of ion has marked influence on the second-order NLO responses. The ßtot values of Cl(-)-buckybowl complexes are all larger as compared to that of Na(+)-buckybowl complexes, which is attributed to the large charge-transfer (CT) from Cl(-) to buckybowl. Our present work will be beneficial for further theoretical and experimental studies on the NLO properties of ion-buckybowl compounds.

##### Assuntos

Íons/química , Modelos Químicos , Hidrocarbonetos Policíclicos Aromáticos/química , Algoritmos , Modelos Moleculares*J Chem Phys ; 145(24): 244705, 2016 Dec 28.*

**| MEDLINE**| ID: mdl-28049323

##### RESUMO

A combined molecular dynamics (MD) and quantum chemical (QC) simulation method is utilized to investigate charge generation mechanism at TTF/TCNQ (tetrathiafulvalene/tetracyanoquinodimethane) heterojunction, which is a controversial donor/acceptor (D/A) interface for organic photovoltaic (OPV) devices. The TTF/TCNQ complexes extracted from MD simulation are classified into parallel and herringbone packings. And then, the amounts of charge transferred from ground states to different excited states and the corresponding energies of charge transfer (CT) state are compared and analyzed using QC simulation. Moreover, the electron transfer/recombination rates for these interfacial configurations are also studied. From these data, we have elucidated the underlying reason why TTF/TCNQ heterojunction is inadaptable to OPV application. One main reason is that large |ΔGCT| (the absolute value of Gibbs free energy change of CT) forms a large energy barrier, limiting exciton dissociation at the TTF/TCNQ heterojunction, and small |ΔGCR| (the absolute value of Gibbs free energy change of charge recombination) performs the easy recombination to the ground state.

*Dalton Trans ; 44(21): 10078-88, 2015 Jun 07.*

**| MEDLINE**| ID: mdl-25948375

##### RESUMO

The electron donor-acceptor complexes, which undergo intramolecular charge transfer under external stimulus, are an emerging class of materials showing important application in nonlinear optics. Synthesizing ferrocene/fullerene complexes through face-to-face fusion would enjoy the merits of both ferrocene and fullerene due to their strong donor-acceptor interactions. Four ferrocene/fullerene hybrid complexes with the gradual extension of fullerene cage size, including CpFe(C60H5), CpFe(C66H5), CpFe(C70H5), and CpFe(C80H5) (Cp is cyclopentadienyl), have been investigated by density functional theory. These hybrid molecules give eclipsed and staggered isomers. The main reason that the eclipsed isomer is stable is that the eclipsed structure possesses large CpFefullerene bonding energy. The CpFefullerene interaction is smaller than that of CpFefullerene, which must come from two different interfaces. The presence of covalent bond character between CpFe and fullerene is supported by the localized orbital locator, deformation of electron density distribution and energy decomposition analysis. Significantly, the absorption bands and first hyperpolarizabilities of these hybrid complexes are strongly sensitive to the fullerene cage size, which is ascribed to a change in the charge transfer pattern, especially for CpFe(C80H5), which displays reverse π â π* charge transfer from bottom to top cage, leading to notable hyperpolarizability. Investigation of the structure-property relationship at the molecular level can benefit the design and preparation of such hybrid complexes in chemistry and materials science.

##### Assuntos

Compostos Ferrosos/química , Fulerenos/química , Metalocenos , Modelos Químicos , Rotação Ocular*J Mol Model ; 21(4): 95, 2015 Apr.*

**| MEDLINE**| ID: mdl-25791353

##### RESUMO

Much effort has been devoted to investigating the molecular geometries, electronic structures, redox properties and nonlinear optical (NLO) properties of Ir complexes involving o-, m- or p-carborane groups by density functional theory (DFT) methods. Switchable second-order NLO properties were induced by redox processes involving these complexes, and it was found that mainly the coordination bonds of Ir complexes changed during the oxidation process. Our calculations revealed that oxidation reactions have a significant influence on the second-order NLO response owing to the change in charge transfer pattern. The ß tot values of oxidized species are at least â¼9 times larger for set I and â¼5 times larger for set II than those of the corresponding parent complexes. Introduction of carborane groups into ppy (phenylpyridine) ligands can enhance the second-order NLO response by 1.2- 1.6 times by a metal-to-ligand charge transfer (MLCT) transition between the Ir atom and carborane. The ß tot of complex 2 [(ppy)2Ir(phen)](+) (phen = phenanthroline) is 3.3 times larger than that of complex 1 (ppy)2Ir(acce) (acce = acetylacetonate), which is caused by ligand-to-ligand charge transfer (LLCT) between ppy ligands and the ancillary ligand. Therefore, it can be concluded that the second-order NLO response can be effectively enhanced by oxidation reactions.

*J Mol Graph Model ; 55: 33-40, 2015 Feb.*

**| MEDLINE**| ID: mdl-25424657

##### RESUMO

Hexathiophenalenylium (HTPLY) has gained increasing attention for its interesting and potentially useful optical properties as a result of the enhancement in spin delocalization and charge-transfer of phenalenyl radicals, occasioned by the attachment of successive three disulfide linkages. Herein, we performed density functional theory to calculate the binding interactions, electronic absorption spectra and the second hyperpolarizabilities of cation and radical dimers of HTPLY and its nitro derivatives. It is found that the equilibrium structures of the π dimers at fully staggered position are most stable. Among these π dimers, radical dimers exhibit stronger binding interactions with respect to cation dimers. In addition, obvious red shifts in electronic spectra of radical dimers are dependent on the large interlayer charge-transfers. More importantly, radical dimers [4]dim3 and [5]dim1 exhibit a significant increase in the second hyperpolarizabilities as compared to cation dimers, which is due to lower excitation energies and larger interlayer charge-transfers. We believe that the results presented in this article shall provide important evidence for the large interlayer charge-transfers in enhancing the NLO properties of the π dimers.

##### Assuntos

Dimerização , Dissulfetos/química , Elétrons , Fenalenos/química , Tiofenos/química , Cátions , Conformação Molecular , Termodinâmica*Dalton Trans ; 43(13): 5069-75, 2014 Apr 07.*

**| MEDLINE**| ID: mdl-24413566

##### RESUMO

The rotary motion based on metallacarboranes around a molecular axis can be controlled by simple electron transfer processes, which provides a basis for the structure-property relationship for the nonlinear optical (NLO) switching. However, this phenomenon has not been previously reported in the development of NLO properties of metallacarboranes. In this work, the metallacarboranes [Ni(III/IV)(C2B9H11)2](-/0) and their C-,B-functionalized derivatives are studied by the density functional theory (DFT) method. By calculating relative energies, we obtained the stable states before and after rotation controlled by simple electron transfer. Then, the static and frequency-dependent second-order NLO properties were calculated by several DFT functionals. According to the TDDFT results, the large NLO responses of the studied compounds are mainly caused by substituent group-to-carborane cage charge transfer (L'LCT) and substituent group-to-metal charge transfer (L'MCT) processes. The order of first hyperpolarizabilities (ß values) illustrates that the NLO response can be enhanced by introducing a strong electron-donating group. Significantly, the geometric interconversions resulting from the redox reaction of 1C/1T-6C/6T allow the NLO responses to be switched "ON" or "OFF". The B(9,9')-methoxyphenyl-functionalized derivative of nickelacarborane, having low energetic cost and large different NLO responses between two states (from 0 to 20 998 a.u.), can be an excellent switchable NLO material.

*Phys Chem Chem Phys ; 16(10): 4900-10, 2014 Mar 14.*

**| MEDLINE**| ID: mdl-24472893

##### RESUMO

The studies of geometrical structures, thermal stabilities, redox properties, nonlinear responses and optoelectronic properties have been carried out on a series of novel ferrocenyl (Fc) chromophores with the view of assessing their switchable and tailorable second order nonlinear optics (NLO). The use of a constant Fc donor and a 4,4'-bipyridinium acceptor and varied conjugated bridges makes it possible to systematically determine the contribution of organic connectors to chromophore nonlinear optical activities. The structures reveal that both the reduction reactions and organic connectors have a significant influence on 4,4'-bipyridinium. The potential energy surface maps along with plots of reduced density gradient mirror the thermal stabilities of the Fc-based chromophores. The first and second reductions take place preferentially at the 4,4'-bipyridinium moieties. Significantly, the reduction processes result in the molecular switches with large NLO contrast varying from zero or very small to a large value. Moreover, time-dependent density functional theory results indicate that the absorption peaks are mainly attributed to Fc to 4,4'-bipyridinium charge transfer and the mixture of intramolecular charge transfer within the two respective 4,4'-bipyridinium moieties coupled with interlayer charge transfer between the two 4,4'-bipyridinium moieties. This provides us with comprehensive information on the effect of organic connectors on the NLO properties.

*J Mol Graph Model ; 48: 28-35, 2014 Mar.*

**| MEDLINE**| ID: mdl-24366003

##### RESUMO

The unusual properties of Li-doped boron nitride nanomaterials have been paid further attention due to their wide applications in many promising fields. Here, density functional theory (DFT) calculations have been carried out to investigate the second-order nonlinear optical (NLO) properties of boron nitride nanocone (BNNC) and its Li-doped BNNC derivatives. The natural bond orbital charge, electron location function, localized orbital locator and frontier molecular orbital analysis offer further insights into the electron density of the Li-doped BNNC derivatives. The electron density is effectively bounded by the Li atom and its neighboring B atoms. The Li-doped BNNC molecules exhibit large static first hyperpolarizabilities (ß(tot)) up to 1.19×10³ a.u. for Li@2N-BNNC, 5.05×10³ a.u. for Li@2B-BNNC, and 1.08×10³ a.u. for Li@BN-BNNC, which are significantly larger than that of the non-doped BNNC (1.07×10² a.u.). The further investigations show that there are clearly dependencies of the first hyperpolarizabilities on the transition energies and oscillator strengths. Moreover, time-dependent DFT results show that the charge transfer from BNNC to Li atom becomes more pronounced as doping the Li atom to BNNC. It is also found that the frequency-dependent effect on the first hyperpolarizabilities is weak, which may be beneficial to experimentalists for designing Li-doped BNNC molecules with large NLO responses.

##### Assuntos

Compostos de Boro/química , Lítio/química , Simulação por Computador , Complexos de Coordenação/química , Modelos Químicos , Modelos Moleculares , Conformação Molecular , Teoria Quântica , Termodinâmica*J Mol Model ; 19(12): 5479-87, 2013 Dec.*

**| MEDLINE**| ID: mdl-24241127

##### RESUMO

The polycyclic p-quinodimethanes are proposed to be the novel candidates of the high-performance nonlinear optical (NLO) materials because of their large third order polarizabilities (Î³). We investigate the switchable NLO responses of a series of polycyclic p-quinodimethanes with redox properties by employing the density functional theory (DFT). The polycyclic p-quinodimethanes are forecasted to exhibit obvious pure diradical characters because of their large y 0 index (the y 0 index is a value between 0 [closed-shell state] and 1 [pure biradical state]). The Î³ values of these polycyclic p-quinodimethanes and their corresponding one-electron and two-electron reduced/oxidized species are calculated by the (U)BHandHLYP method. The Î³ values of polycyclic p-quinodimethanes and their corresponding one-electron reduced species are all positive and significantly different. The large differences of the Î³ values are due to a change in the transition energy and are related to the different delocalization of the spin density, which demonstrates that the NLO switching is more effective on one-electron reduction reactions. Therefore, the study on these polycyclic p-quinodimethanes provides a guideline for a molecular design of highly efficient NLO switching.

*J Phys Chem A ; 117(47): 12497-510, 2013 Nov 27.*

**| MEDLINE**| ID: mdl-24180267

##### RESUMO

The second-order nonlinear optical (NLO) properties of a series of Pt(II) dithienylethene (DTE) complexes possessing the reversible photochromic behavior have been investigated by density functional theory (DFT) combined with the analytic derivatives method. The results show that the calculated static first hyperpolarizabilities (ßtot) of the open-ring and closed-ring systems significantly increase in the range of 2.1-4.5 times through strengthening of the electron-withdrawing ability of the substituent R (R = H, CF3, NO2) and an increase of the number of thiophene rings. Moreover, there is a large enhancement of the ßtot values from the open-ring systems to the corresponding closed-ring systems. This efficient enhancement is attributed to the better delocalization of the π-electron system, the more obvious degree of charge transfer, and the larger f(os)/E(gm)(3) (f(os) is the oscillator strength, and E(gm) is the transition energy between the ground and the excited states) values in the closed forms according to the bond length alternation (BLA) and time-dependent density functional theory (TDDFT) calculations. In addition, the dispersion has less influence on the frequency-dependent first hyperpolarizabilities (ßtot(ω)) of the studied systems at the low-frequency area ω (0.000-0.040 au). Our present work would be beneficial for further theoretical and experimental studies on large second-order NLO responses of metal complexes.

##### Assuntos

Compostos Organoplatínicos/química , Tiofenos/química , Estrutura Molecular , Fenômenos Ópticos , Processos Fotoquímicos , Teoria Quântica*J Chem Phys ; 139(12): 124314, 2013 Sep 28.*

**| MEDLINE**| ID: mdl-24089774

##### RESUMO

An increasing number of chemists have focused on the investigations of two-electron/multicenter bond (2e/mc) that was first introduced to describe the structure of radical dimers. In this work, the dimerization of two isoelectronic radicals, triazaphenalenyl (TAP) and hexaazaphenalenyl (HAP) has been investigated in theory. Results show TAP2 is a stable dimer with stronger 2e/12c bond and larger interaction energy, while HAP2 is a less stable dimer with larger diradical character. Interestingly, the ultraviolet-visible absorption spectra suggest that the dimerization induces a longer wavelength absorption in visible area, which is dependent on the strength of dimerization. Significantly, the amplitude of second hyperpolarizability (Î³(yyyy)) of HAP2 is 1.36 × 10(6) a.u. that is larger than 7.79 × 10(4) a.u. of TAP2 because of the larger diradical character of HAP2. Therefore, the results indicate that the strength of radical dimerization can be effectively detected by comparing the magnitude of third order non-linear optical response, which is beneficial for further theoretical and experimental studies on the properties of complexes formed by radical dimerization.

*J Mol Graph Model ; 41: 79-88, 2013 Apr.*

**| MEDLINE**| ID: mdl-23500631

##### RESUMO

The third-order nonlinear optical (NLO) properties of aromatic diimide molecules have been studied for the first time using density functional theory (DFT) with a finite field (FF). This study shows that the size of the aromatic core can affect the static second hyperpolarizability (Î³). Increasing the number of benzenes along the longitudinal axis can effectively improve the Î³ values because the degree of charge transfer along the longitudinal direction increases, whereas an increase in the number of benzenes along the perpendicular axis does not enhance the Î³ values. Furthermore, the NLO responses of the reduced form radical anions 1(-), 5(-) and 6(-), which were obtained by a reversible redox process, are discussed. The results show that the Î³ values of the radical anions are changed by the redox process. For the reduced form radical anion 6(-), the Î³ value is -1906.71×10(-36)esu, and its absolute value is â¼7.3 times larger than that of its neutral parent. An analysis of the BLA values demonstrates that the Î³ value is closely related to the conjugation of the aromatic core used in the redox process.

##### Assuntos

Derivados de Benzeno/química , Radicais Livres/química , Imidas/química , Ânions , Modelos Químicos , Dinâmica não Linear , Oxirredução , Teoria Quântica , Eletricidade Estática*J Mol Model ; 19(4): 1779-87, 2013 Apr.*

**| MEDLINE**| ID: mdl-23306734

##### RESUMO

As a kind of novel organometallic complexes, the cyclopentadienylcobalt (CpCo) linear [4]phenylene complexes (4 = number of benzene rings) display efficient switchable nonlinear optical (NLO) response when CpCo reversibly migrates along the linear [4]phenylene triggered by heating or lighting. In this paper, the second-order NLO properties for CpCo linear [4]phenylene complexes were calculated by using the density functional theory (DFT) methods with four functionals. All of the functionals yield the same order of ß tot values: 1<2<4<3. The effect of solvent on second-order NLO properties has been studied using polarized continuum model (PCM) in the tetrahydrofuran (THF) solution. The solvent leads to a slight enhancement of the NLO responses for the studied complexes relevant to their NLO responses in vacuo. The electronic absorption spectra were investigated by the TDDFT methods. The TDDFT calculations indicate that the maximum absorption peaks of complexes 2-4 in the near-infrared spectrum area show the bathochromic shift together with a decreasing intensity compared to complex 1. We have also found that the cobalt (Co) atom acts as a donor in all the organometallic complexes and the d â π* and π â π* charge transfer (CT) transitions contribute to the enhancement of second-order NLO response. Furthermore, two experimentally existing complexes 1 and 3 are found to have a large difference in ß tot values. It is our expectation that this difference may stimulate the search for a new type of switchable NLO material based on CpCo linear [4]phenylene complexes.

*Phys Chem Chem Phys ; 14(47): 16476-85, 2012 Dec 21.*

**| MEDLINE**| ID: mdl-23131708

##### RESUMO

Stimulated by the preparation and characterization of the isolated pentagon rule (IPR) violating chlorofullerene: C(60)Cl(8) (Nat. Mater. 2008, 7, 790-794), we have performed a systematic investigation on the structural stabilities, electronic and optical properties of the IPR-violating C(60)X(8) (X = H, F, and Cl) fullerene compounds via density functional theory. The large energy gaps between the highest occupied and the lowest unoccupied molecular orbitals provide a clear indication of high chemical stabilities of C(60)X(8) derivatives, and moreover, the C(60)X(8) molecules present great aromatic character with the negative nucleus independent chemical shift values. In the addition reactions of C(60) (C(2v)) + 4X(2) â C(60)X(8), a series of exothermic processes are involved, with high reaction energies ranging from -71.97 to -233.16 kcal mol(-1). An investigation on the electronic property shows that C(60)F(8) and C(60)Cl(8) could be excellent electron acceptors as a consequence of large vertical electron affinities. The density of state analysis suggests that the frontier molecular orbitals of C(60)X(8) are mainly from the carbon orbitals of two separate annulene subunits, and the influence from X atoms is secondary. In addition, the ultraviolet-visible spectra and second-order hyperpolarizabilities of C(60)X(8) are calculated by means of time-dependent density functional theory and a finite field approach, respectively. Both the average static linear polarizability <α> and second-order hyperpolarizability <Î³> of C(60)X(8) increase greatly compared to those of C(60).

*J Phys Chem A ; 116(43): 10496-506, 2012 Nov 01.*

**| MEDLINE**| ID: mdl-23050877

##### RESUMO

The static second-order nonlinear optical (NLO) properties on a series of the two-dimensional (2D) pincer Ru(II) complexes with the substituted Tpy and H(2)SCS tridentate ligands (Tpy = 2,2':6',2â³-terpyridyl and H(2)SCS = 2,6-bis(benzylaminothiocarbonyl)phenyl) have been investigated by density functional theory (DFT). Introducing different donor/acceptor substituents to two ligands has an influence on the static first hyperpolarizabilities (ß(tot)) of the 2D systems. Compared to the reference system 1 [Ru(H(2)SCS)(Tpy)](+), introducing the branches with strong electron acceptor group (p-NO(2)-phenylethynyl) to the Tpy ligand or the branches with strong electron donor group (p-NH(2)-phenylethynyl) to the H(2)SCS ligand can effectively improve the ß(tot) values. Time-dependent DFT (TDDFT) calculations indicate that the enhanced ß(tot) values of the substituted systems are dominated by the intraligand charge transfer (ILCT), metal-to-ligand charge transfer (MLCT) and ligand-to-metal charge transfer (LMCT) transitions. Furthermore, the proton abstraction plays an important role in tuning the second-order NLO response. Particularly, for system 5 bearing the branches with NO(2) groups on H(2)SCS ligand, there is a dramatic enhancement in the ß(tot) values for its deprotonated forms. The ß(tot) values of the monodeprotonated system 5-H and the dideprotonated system 5-2H (58.712 × 10(-30) and 761.803 × 10(-30) esu) are about 7.58 times and 36.4 times larger than their diprotonated system 5, respectively. The second-order NLO responses based on substituent effect and proton abstraction switch are two-dimensional in characteristic with the large off-diagonal tensor values.