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Recently, both lithium (Li) salts and Li electrides formed by one Li atom interacting with ligand complexes, have been widely investigated. An interesting question emerges: is the configuration of one Li atom interacting with ligand complexes a Li salt or electride? In the present work, four configurations n-Li-PNA ( n = 1-4) were obtained by binding one Li atom with the p-nitroaniline (PNA) at different positions to explore this question. The results show that 1-Li-PNA and 2-Li-PNA are typical Li salts, and 4-Li-PNA is a typical Li electride. Significantly, 3-Li-PNA possesses both characteristics of Li salt and electride. At the same time, 3-Li-PNA has the largest first hyperpolarizability (2.9 × 10 au) by ROMP2 method compared with the other three configurations. Furthermore, the first hyperpolarizability of 3-Li-PNA is about 2600 times larger than that of PNA. Further, the vertical ionization potential (VIP) and interaction energy ( E) indicate that 3-Li-PNA is less stable than 1-Li-PNA and 2-Li-PNA (Li salts), but is more stable than 4-Li-PNA (Li electrides). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

This study spotlights the fundamental insights about the structure and static first hyperpolarizability ( β) of a series of 2,4-dinitrophenol derivatives (1-5), which are designed by novel bridging core modifications. The central bridging core modifications show noteworthy effects to modulate the optical and nonlinear optical properties in these derivatives. The derivative systems show significantly large amplitudes of first hyperpolarizability as compared to parent system 1, which are 4, 46, 66, and 90% larger for systems 2, 3, 4, and 5, respectively, at Moller-Plesset (MP2)/6-31G* level of theory. The static first hyperpolarizability and frequency dependent coupled-perturbed Kohn-Sham first hyperpolarizability are calculated by means of MP2 and density functional theory methods and compared with respective experimental values wherever possible. Using two-level model with full-set of parameters dependence of transition energy (Δ Ε), transition dipole moment ( μ0) as well as change in dipole moment from ground to excited state (Δ μ), the origin of increase in β amplitudes is traced from the change in dipole moment from ground to excited state. The causes of change in dipole moments are further discovered through sum of Mulliken atomic charges and intermolecular charge transfer spotted in frontier molecular orbitals analysis. Additionally, analysis of conformational isomers and UV-Visible spectra has been also performed for all designed derivatives. Thus, our present investigation provides novel and explanatory insights on the chemical nature and origin of intrinsic nonlinear optical (NLO) properties of 2,4-dinitrophenol derivatives. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In the current work, a series of bithiopheneimide (BTI)-based D–A copolymers were investigated based on the reported PDTSBTI (1) to screen excellent molecules toward organic photovoltaic (OPV) donor materials. It is found that the PCE based on the proposed derivative 4, where the silicon atom is replaced with vinyl and cyano groups on the DTS unit, shows a 70 percent improvement by Scharber diagrams compared with its prototype 1. Then, the charge transfer dynamics of 1/PC71BM and 4/PC71BM were investigated, including the intermolecular charge transfer (inter-CT) and recombination (inter-CR) rates. The theoretical data demonstrate that the ratio kinter-CT/kinter-CR of 4/PC71BM heterojunction is about 1 × 105 times higher than that of 1/PC71BM. These results clearly reveal that the designed donor molecule 4 will be a promising candidate for high-performance OPV device. We expect that this work from electron processing at the D/A interface may provide a theoretical guideline for further optimization and design of organic copolymer donor materials. [ABSTRACT FROM AUTHOR]

In the present work, three complexes(1-Li–NO 2 , 1-Li-Mid and 1-Li–NH 2 ) were designed by doping Li atom into the different location(above, middle and below) of the novel noncovalent “through-space” electronic interaction (S) of Donor-S-Acceptor (1) to explore their structure-property relationships. The results show that doping Li atom can obviously enhance the first hyperpolarizability (β tot) of 1. Interestingly, the crucial transition direction of 1-Li–NH 2 is from donor group to acceptor group, which is opposite to those of 1-Li–NO 2 and 1-Li-Mid. The highest occupied molecular orbital (HOMO) of 1-Li–NH 2 shows that doping one Li atom enhances the π–π interaction resulting in the largest β tot value (1.50 × 105) which is about 16 times larger than that of 1(9.13 × 103) and is also obviously larger than those of 1-Li-Mid(5.81 × 104) and 1-Li–NO 2 (6.45 × 104 au). The results indicate that 1-Li–NH 2 can be considered as a novel high-performance NLO material and the location of Li atom can modulate NLO response. [ABSTRACT FROM AUTHOR]

Due to the unusual properties of the Möbius cyclacenes (MC) such as π electrons, MC has drawn the extensive attention of scientists. In the present work, six [ n]MC ( n = 13-18, n is the number of benzenoid rings) were systematically investigated to explore the size-dependent effects on structures, electro-optical properties, and frontier molecule orbits (FMO). According to the dihedral angles (C-C-C-C), the un-twisted area and twisted area are defined, respectively. The twisted area mainly distributes on seven or eight benzenoid rings for [ n]MC ( n = 13-18). Further, the polarizability ( α) and first hyperpolarizability ( β) of [ n]MC ( n = 13-18) were calculated with three density functional methods (BHandHLYP, Cam-B3LYP, and M06-2X). Results show that the α values increase linearly with increasing the number ( n) of benzenoid rings. Significantly, the β values are increased to zigzag with increasing the number ( n) of benzenoid rings. Interestingly, when n is even ( 14, 16, and 18), the electron transfer is from the twisted area to the un-twisted area, but the electron transfer is from the un-twisted area to the twisted area when n is odd ( 13, 15, and 17). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) materials are the smartest materials of the era, and have the ability to generate new electromagnetic fields with changed frequencies, phases, and other physical properties. Recently, many cutting edge research reports have been focused on NLO materials especially on those which are composed of sp2 hybridized carbon nanostructures. As the carbon nanostructures are composed of abundant π-electrons and have significant delocalization, these are potential candidates for modern NLO materials. Generally, sp2 hybridized carbon nanostructures can be divided into zero-dimensional fullerenes, one-dimensional nanotubes and two-dimensional graphene nanoribbons and quantum dots etc. These dimensionally different carbon nanomaterials are promising candidates for a wide range of applications in next-generation nanotechnologies. In present feature article, we first briefly explain a theoretical structure–NLO property relationship based on perturbation theory and then elucidate the crucial factors to control the NLO responses. We put together the different random investigations of sp2 hybridized carbon nanostructures for NLO application by highlighting the importance of their several structural designs to tune NLO amplitudes. Furthermore, we make a comparative and updated analysis of the NLO properties of dimensionally different sp2 hybridized carbon nanomaterials i.e. fullerenes, carbon nanotubes, and graphene nanoribbons and quantum dots. Finally, we make a brief discussion about different aspects and opportunities to use the sp2 hybridized carbon nanomaterials as high performance NLO materials of the future. This review is a focused perspective based on different updated quantum chemical investigations about fullerenes, nanotubes and graphene nanoribbons and quantum dots for their possible use in nonlinear optical applications. [ABSTRACT FROM AUTHOR]

The unusual properties of thiophene-fused benzocarborane have attracted a lot of interest in recent years due to their wide applications in photonics and optoelectronics. In the present work, nine molecules [M, N] (M, N are labeled as the number of thiophene rings on the left and right part, respectively) on the basis of thiophene-fused benzocarborane were considered. The first hyperpolarizability ( β) values of three synthesized symmetric molecules [1, 1], [2, 2], [3, 3] (M=N, Chem. Eur. J 2012. 18, 11251-11257) and six asymmetric molecules [1, 2], [1, 3], [1, 4], [1, 5], [2, 3], [2, 4] (M≠N) were investigated, β values of symmetric molecules show the order: 39 of [1, 1]< 800 of [2, 2]< 903 au of [3, 3], which indicate that β value increases with increasing the number of thiophene ring for symmetric molecules. The other order of β values can be observed: 39 of [1, 1]< 800 of [1, 2]< 3553 of [1, 3]< 7998 of [1, 4]< 13049 au of [1, 5] and 66 of [2, 2]< 3240 of [2, 3]< 8029 au of [2, 4]. Interestingly, when sum of M and N is constant, larger difference between M and N is, larger β value is: 800 au of [2, 2]< 3553 au of [1, 3]; 3240 au of [2, 3] < 7998 au of [1, 4]; 903 au of [3, 3]< 8029 au of [2, 4]< 13049 au of [1, 5]. Significantly, [1, 5] with six thiophene rings has the largest β value (13049 au) which is greatly larger than 903 au of [3, 3] with six thiophene rings. Furthermore, the natural bond orbital (NBO) charge populations, the nucleus-independent chemical shift (NICS), the bond length alternation (BLA) of the nine molecules and crucial transition were studied in our work. We hope that the present work will be beneficial for future theoretical and experimental studies on the electro-optical properties of thiophene-fused benzocarborane molecules. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Recently, the extreme learning machine neural network (ELMNN) as a valid computing method has been proposed to predict the nonlinear optical property successfully (Wang et al., J. Comput. Chem. 2012, 33, 231). In this work, first, we follow this line of work to predict the electronic excitation energies using the ELMNN method. Significantly, the root mean square deviation of the predicted electronic excitation energies of 90 4,4-difluoro-4-bora-3 a,4 a-diaza- s-indacene (BODIPY) derivatives between the predicted and experimental values has been reduced to 0.13 eV. Second, four groups of molecule descriptors are considered when building the computing models. The results show that the quantum chemical descriptions have the closest intrinsic relation with the electronic excitation energy values. Finally, a user-friendly web server (EEEBPre: Prediction of electronic excitation energies for BODIPY dyes), which is freely accessible to public at the web site: http://202.198.129.218, has been built for prediction. This web server can return the predicted electronic excitation energy values of BODIPY dyes that are high consistent with the experimental values. We hope that this web server would be helpful to theoretical and experimental chemists in related research. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In the present work, Li@porphyrins and their derivatives were designed in order to explore the effect of dehydrogenation/hydrogenation on linear and nonlinear optical properties. Their stable structures were obtained by the M06-2X method. Moreover, the M06-2X method showed that dehydrogenation/hydrogenation has greatly influences polarizabilities ( α values) and hyperpolarizabilities ( β and γ values): α values ranged from 331 to 389 au, β values from 0 to 2465 au, and γ values from −21.2 × 10 to 21.4 × 10 au. This new knowledge of the effect of dehydrogenation/hydrogenation on nonlinear optical properties may prove beneficial to the design and development of high-performance porphyrin materials. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In view of their intriguing structural and electrical properties, the linear and nonlinear optical (NLO) responses of six carbon nanotube (CNT) molecules substituted by nitrogen atoms at one end have been explored by using the CAM-B3LYP method. Molecules 1, 2 and 3 were obtained by increasing the lengths of the CNTs, and 1-Li, 2-Li and 3-Li were constructed by doping one Li atom into the N-substituted end of 1, 2 and 3 (mentioned above), respectively. Two effective approaches have been proposed to increase nonlinear optical properties(NLO): increasing the length of the CNT as well as doping one Li atom into the N-substituted end. The results show that both the linear polarizabilities ( α) and nonlinear first hyperpolarizabilities ( β) values increase with increasing the lengths of the CNTs: 188 of 1 < 307 of 2 < 453 of 3 for α and 477 of 1 < 2654 of 2 < 3906 au of 3 for β. Significantly, compared with the non-doped CNTs, the β values are remarkably enhanced by doping one Li atom into the N-substituted end: 477 of 1 < 23258 of 1-Li, 2654 of 2 < 37244 of 2-Li, and 3906 of 3 < 72004 au of 3-Li. Moreover, the β values show a similar trend to the β values. Our results may be beneficial to experimentalists in exploring high-performance nonlinear optical materials based on CNT. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Six N-substituted [ n]cyclacene ( n = 5, 6, 7,...,10) molecules were designed to study the relationship between the structure and first hyperpolarizability. Their static first hyperpolarizabilities ( β0) were obtained by MP2/6-31 + g(d) level. Two interesting relationships between the β0 value and the structure have been found: (1) The β0 value increases with the increase of the number n when n is odd: 3155 ([5]cyclacene) < 48,905 ([7]cyclacene) < < 393,444 ([9]cyclacene), and when n is even: 357,620 ([6]cyclacene) < 618,608 ([8]cyclacene) < 3,513,644 a.u. ([10]cyclacene). (2) The β0 values (in the range of 357,620 ~ 3,513,644 a.u.) of the N-substituted [ n]cyclacene (when n is odd) are much larger (in the range of 3155~393,444 a.u.) than that of the N-substituted [ n]cyclacene (when n is even). Furthermore, their frequency-dependent β (−2ω; ω, ω) and β (−ω; ω, 0) (ω = 0.005, 0.01, and 0.0239 a.u.) were also estimated by Møller-Plesset perturbation/6-31 + g(d) level. Among the frequency-dependent β (ω), [10]cyclacene has the largest β (−ω; ω, 0) and β (−2ω; ω, ω) to be 1.2 × 108 (ω = 0.01) and 2.9 × 107 a.u. (ω = 0.005 a.u.), which are much larger than the static β0 = 3.5 × 106 a.u. by 34 and 8 times. Our present work may offer a new idea in the design of high-performance tubiform nonlinear optical materials. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The proper theoretical calculation method for nonlinear optical (NLO) properties is a key factor to design the excellent NLO materials. Yet it is a difficult task to obatin the accurate NLO property of large scale molecule. In present work, an effective intelligent computing method, as called extreme learning machine-neural network (ELM-NN), is proposed to predict accurately the first hyperpolarizability (β0) of alkalides from low-accuracy first hyperpolarizability. Compared with neural network (NN) and genetic algorithm neural network (GANN), the root-mean-square deviations of the predicted values obtained by ELM-NN, GANN, and NN with their MP2 counterpart are 0.02, 0.08, and 0.17 a.u., respectively. It suggests that the predicted values obtained by ELM-NN are more accurate than those calculated by NN and GANN methods. Another excellent point of ELM-NN is the ability to obtain the high accuracy level calculated values with less computing cost. Experimental results show that the computing time of MP2 is 2.4-4 times of the computing time of ELM-NN. Thus, the proposed method is a potentially powerful tool in computational chemistry, and it may predict β0 of the large scale molecules, which is difficult to obtain by high-accuracy theoretical method due to dramatic increasing computational cost. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011 [ABSTRACT FROM AUTHOR]

Abstract: The 89 classical C44 isomers, its anions and derivatives such as C44X n (X=H, F, and Cl; n =14 and 16) and M@C44 (M=He, Li, and Ca) have been systematically investigated by ab initio and density function methods. Although the D 2:75 species has the least number of adjacent pentagons, the MP2 geometry optimizations suggest that the D 3 h :72 structure is favored by ∼11kcal/mol over the D 2:75 isomer. Systematic investigations of the electronic properties show that neutral D 3 h :72 is highly aromatic. In contrast, the two lowest energy isomers of , D 2:75 and D 2:89, are highly aromatic. Compared with C50X10 (D 5 h ), the large energy gaps and the aromatic character of C44X14 (D 3 h :72) indicate that they possess high stabilities. Furthermore, the predicted reaction energies of C44X14 (D 3 h :72) derivatives are highly exothermic, suggesting a considerable possibility for experimental realization. Investigations also show that the D 2:75 endohedral structure is most stable for Ca@C44. [Copyright &y& Elsevier]

In our previous work, new alkalides Li+(calix [4]pyrrole)M− with cup‐like complexant have been reported for the large static first hyperpolarizabilities (β0) (Chen et al., J Am Chem Soc 2006, 128, 1072). In this work, new inorganic alkalides are found by using a more flexible complexant, methylamine (NH2CH3)4. The structures with all real frequencies and β0 values of the inorganic alkalides Li+(cage [4]methylamine)M− (M = Li, Na, and K) are obtained at MP2 level. The result shows that these inorganic alkalides have more considerable β0 values to be 18,825 (M = Li) < 27,942 (M = Na) < 81,094 au (M = K), which are more than two times larger than those (10,969 ∼ 35,934 au) of the reported alkalides Li+(calix [4]pyrrole)M−. To understand this structure–property relationship, two cup‐like Li+(NH2CH3)4M− (M = Li, Na, and K) models are designed to compare their β0 values. By comparing the β0 values among the cup‐like alkalides Li+(calix [4]pyrrole)M−, Li+(NH2CH3)4M−, and cage‐like alkalides Li+(cage [4]methylamine)M− (M = Li, Na, and K), the complexant shape effect of alkalides has been revealed. It is found that the complexant shape is an important factor in large β0 values. Moreover, the monotonic dependences of β0 on the Li–M distance and the NBO charges of cation (Li+) and anions (M−) in inorganic alkalides Li+(cage [4]methylamine)M− have been shown. In this work, the frequency dependent first (hyper)polarizabilities are also determined. It is found that both the frequency dispersion and the effects of the electron correlation are strong. Moreover, the dependence of both the static and frequency dependent β on the atomic number of alkali metal anions is similar. This work provides a new way to understand the nature of high‐performance nonlinear optical (NLO) materials, and it is helpful to design new NLO materials. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011. [ABSTRACT FROM AUTHOR]