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An operationally simple protocol is described for the facile, modular and regioselective access of all-pyrano-moiety-substituted iminochromenes, particularly under undried acetonitrile and air atmosphere.

Engineering the preorganization of photoactive units remains a big challenge in solid-state photochemistry research. It is of not only theoretical importance in the construction of topochemical reactions but also technological significance in the fabrication of advanced materials. Here, a cyanostilbene derivative, (Z)-2-(3,5-bis(trifluoromethyl)phenyl)-3-(naphthalen-2-yl) acrylonitrile (BNA), was crystallized into two polymorphs under different conditions. The two crystals, BNA-α and BNA-β, have totally different intra-π-dimer and inter-π-dimer hierarchical architectures on the basis of a very simple monomer, which provides them with distinct reactivities, functions and photoresponsive properties. Firstly, two different types of solid-state [2 + 2] photocycloaddition reaction: (i) a typical olefin–olefin cycloaddition reaction within the symmetric π-dimers of BNA-α and (ii) an unusual olefin-aromatic ring cycloaddition reaction within the offset π-dimers of BNA-β have been observed, respectively. Secondly, the crystal of BNA-α can be bent to 90° without any fracture, exhibiting outstanding flexibility upon UV irradiation, while the reversible photocycloaddition/thermal cleavage process (below 100 °C) accompanied by unique fluorescence changes can be achieved in the crystal of BNA-β. Finally, micro-scale photoactuators and light-writable anti-counterfeiting materials have been successfully fabricated. This work paves a simple way to construct smart materials through a bottom-up way that is realized by manipulating hierarchical architectures in the solid state., Two crystals with different hierarchical architectures are observed based on a single molecule, achieving different types of [2 + 2] photocycloaddition. Finally, controllable photoactuators and light-writable materials are successfully fabricated.

The sluggish kinetics and unclear mechanism have significantly hindered the development of Li-CO2 batteries. Here, a Li-CO2 battery cathode catalyst based on a porphyrin-based covalent organic framework (TTCOF-Mn) with single metal sites is reported to reveal intrinsic catalytic sites of aprotic CO2 conversion from the molecular level. The battery with TTCOF-Mn exhibits a low overpotential of 1.07 V at 100 mA/g as well as excellent stability at 300 mA/g, which is one of the best Li-CO2 battery cathode catalysts to date. The unique features of TTCOF-Mn including uniform single-Mn(II)-sites, fast Li+ transfer pathways, and high electron transfer efficiency contribute to effective CO2 reduction and Li2CO3 decomposition in the Li-CO2 system. Density functional theory calculations reveal that different metalloporphyrin sites lead to different reaction pathways. The single-Mn(II) sites in TTCOF-Mn can activate CO2 and achieve an efficient four-electron CO2 conversion pathway. It is the first example to reveal the catalytic active sites and clear reaction pathways in aprotic Li-CO2 batteries.

Iridium-catalyzed C–H borylation of THF was theoretically investigated as example of sp3 C–H functionalization. DFT computations show that β-regioselective borylation occurs more easily than does α-regioselective, as reported experimentally, through oxidative addition of C–H bond to iridium(III) species and reductive elimination of B–C bond. The reductive elimination is both a rate-determining step and a regioselectivity-determining step. The lower energy transition state (TS) of the reductive elimination of β-boryloxolane arises from the Ir···(β-oxolanyl) interaction at TS being stronger than the Ir···(α-oxolanyl) one. The Ir···(β-oxolanyl) interaction being stronger than the Ir···(α-oxolanyl) one is a result of the valence orbital energy of the α-oxolanyl group being higher than that of the β-oxolanyl group due to antibonding overlap of the valence orbital with O 2p orbital, where SOMO of oxolanyl radical is taken as valence orbital hereinafter. Reactivity of substrate decreases following the order prim...

Methane borylation catalyzed by Cp*M(Bpin)n (M = Ru or Rh; HBpin = pinacolborane; n = 2 or 3) and (TMPhen)Ir(Bpin)3 (TMPhen = 3,4,7,8-tetramethyl-1,10-phenanthroline) was investigated by DFT in com...

The efficient regioselective C-H cyanoalkoxylation and cyanoalkylation of 8-aminoquinoline derivatives at the C5 position have been achieved under O2 and N2 atmospheres, respectively. Using 2,2'-azobisisobutyronitrile (AIBN) as a radical precursor, the protocols afforded the corresponding products in moderate to good yields with broad substrate generality through Cu(OAc)2 or NiSO4 catalysis. Furthermore, the single electron transfer (SET) mechanism was proposed via a radical coupling pathway.

N-Heterocyclic carbene (NHC) ligands effective for the cross-coupling of nitroarenes were identified. A rational design of the NHC ligand structures enabled significant reduction of catalyst loadings compared with the previous system employing BrettPhos as a phosphine ligand. Experimental and theoretical studies to compare these ligands gave some insights into high activity of the newly developed NHC ligands.

An external electric field (EEF), as a metal-free catalyst, catalyzing the Markovnikov hydrosilylation of styrene was studied for the first time. As compared to the field-free situation, the barrier height was almost halved upon the application of EEF with a field strength of 180 × 10−4 a.u. in the direction perpendicular to the “bond axis”. Therefore, the use of EEF not only resolved the questions of the separation of homogeneous catalysts from the reaction mixture, but also facilitated the reaction by decreasing its barriers. Furthermore, we found that the lower the energy of the transition state (TSX) and the higher the energy of the HOMO of the reactant (R1′), the lower the barrier height of hydrosilylation. Hopefully, this study can provide guidance toward experiments involving an external electric field.

The strong adsorption stability and significantly improved incident photon-to-current conversion efficiency (IPCE) of the new anchoring group hydantoin moiety (HY) introduced into D-A-π-A dyes for dye sensitized solar cells (DSSCs), compared with the commonly used anchoring group cyanoacrylic acid (CA), were investigated through DFT/TD-DFT calculations on the dye@(TiO2)48 interfacial electron dynamics for the first time. It is found that the dissociative bidentate bridging mode with a hydrogen bond is the most stable adsorption configuration on the TiO2 anatase (101) surface for HY-based dyes and could produce a dramatic increase in adsorption energy compared with that of CA-based dye. Energy decomposition analysis (EDA) was performed to elucidate the different adsorption energies for the different anchoring groups with different adsorption configurations. A simplified Tamm-Dancoff density functional theory approach (sTDA-DFT), proposed by Grimme, was used to calculate the excitation energy and oscillator strength of the sensitizers after adsorption. The calculated results indicate that the adsorption mode has significant effects on the absorption spectrum. In contrast to CA-based dye, HY-based dye exhibits comparable light harvesting ability after adsorption due to the combined effects of different adsorption configurations, although the isolated dye exhibits a blue-shifted absorption spectrum. It shows a similar electron injection and dye regeneration driving force, but the significantly larger coupling between the sensitizer and the semiconductor for HY-based dye is the main reason for its improved IPCE. Moreover, to further improve the light-harvesting ability of the dyes, two other heterocyclic groups, rhodanine (RD) and 2-(3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile (MT), were introduced into the dyes as anchoring groups. The results show that dyes with the RD anchoring group exhibited significantly enhanced light harvesting ability with the red-shifted absorption spectrum, higher electron injection efficiency with larger electronic coupling and strong adsorption ability; thus, it is worthy of experimental synthesis for use in high-performance dye sensitized solar cells.

Synthesis of biaryls via the Suzuki–Miyaura coupling (SMC) reaction using nitroarenes as an electrophilic coupling partners is described. Mechanistic studies have revealed that the catalytic cycle of this reaction is initiated by the cleavage of the aryl–nitro (Ar–NO2) bond by palladium, which represents an unprecedented elemental reaction.

In this work, by combining the superiority of polyoxometalates (POMs) and catalytic single-metal site Co of metalloporphyrin, a series of mixed-valence POM-based metal-organic frameworks (MOFs) composites is synthesized by a post-modification method. The electron-transfer property of POM@PCN-222(Co) composite is significantly enhanced owing to the directional electron-transfer from POM to single-metal site Co in PCN-222(Co). In particular, H-POM@PCN-222(Co) gives a high Faradaic efficiency of 96.2% for electroreduction of CO2 into CO and good stability over 10 h. DFT calculations confirm that the directional electron transfer, which accelerates the multi-electron transfer from the electrode to active single-metal site Co, enriches the electron density of the Co center, and ultimately reduces the energy of the rate-determining step, thus increasing the catalytic activity of CO2 reduction reaction (CO2 RR). This work therefore suggests some new insight for the design of efficient electrocatalysts for CO2 RR.

For a photochromic spiro-diarylethene derivative (Spiro-DAE), its photocyclization reaction and multicolour fluorescence modulation performances were investigated based on a series of density functionals calculations in this work. Some elementary properties such as geometric and electronic structures at ground and the first excited state (S1), absorption and emission spectra in respective open-ring and closed-ring structures were compared, which indicate the cyclization reaction may occur at S1. It is further verified by the lower activation barrier (3.4 kcal/mol) of the transition state at S1 potential energy surface. The photochromic reaction rates for both cyclization and cycloreversion processes were quantitatively estimated, which suggests the much smaller radiative and internal conversion rates contribute to the higher photocyclization rate and thus efficiency. Furthermore, we suspect that the dihydroacridine fragment may make important contribution to the cyclization reaction occurring at S1 considering its contribution to electronic structure.

In this study, density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations were employed to investigate the geometries, electronic structures, reorganization energy (λ) and photophysical properties of four cyclometalated Pt(II) complexes (bzq)Pt(dpm) (1), (bzq)Pt(ppy) (2), (bzq)Pt(Ncaz) (3) and (bzq)Pt(Ndbt) (4) (where bzq = benzo[h]quinoline, dpm = dipivolylmethanoate, ppy = 2-phenylpyridine, Ncaz = N-substituted carbazole and Ndbt = N-substituted dibenzothiophene). In addition, the radiative decay processes and zero-field splitting were calculated based on the spin–orbit coupling (SOC) effect, and nonradiative decay pathways were discussed to evaluate the phosphorescence efficiency qualitatively. All the complexes retain the bzq as a cyclometalated ligand and our research focuses on the role recognition of another ancillary ligand modification theoretically. According to the results, in complexes 2–4 replacing the dpm with different ligands shows better rigidity which may weaken the nonradiative decay pathways and enhance the capability of charge transfer. Furthermore, complexes 1–4 tend to be bluish-green luminescent materials, and the emission wavelengths of 1, 2 and 4 are close to each other due to the similar excited state energy levels and electronic density distribution. Compared with complex 1, the radiative decay rate constants (kr) of 2–4 are greatly increased. Therefore, the designed complexes would be potential phosphorescence materials because of their high phosphorescence quantum efficiency and complex 3 can also serve as a promising bipolar transporting material due to its better charge transfer balance character.

The special iron(II) polypyridyl complex substituted by fluorine ([Fe(dftpy)2]2+, dftpy = 6,6″-difluoro-2,2’; 6′2″-terpyridine) with uncommon mixed ground states has been detected recently, but the related explanation and characterization are not enough, especially for the influence of substituents. On the basis of previous studies, the key problem of mixed spin states is expected to be described very well by means of theoretical calculations. In this work, density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations have been carried out to study the characteristics of the excited states in detail. Comparing with the parent complex [Fe(tpy)2]2+ (tpy = 2,2′:6′,2″-terpyridine) and corresponding bromine or chlorine substituted derivates, the ground states of [Fe(dftpy)2]2+ stay around the mixture of singlet state and quintet state, but also there is rare high spin excited state lifetime. Among the halogen substituted complexes, [Fe(dftpy)2]2+ has the shortest MLCT state lifetime of 14.0 ps which has been much longer than subpicosecond lifetime of [Fe(tpy)2]2+. The reason is explored by the combination of electronic structures, absorption properties, extended transition state coupled with natural orbitals for chemical valence (ETS-NOCV) and potential energy curves (PECs). We can find that the bond lengths of Fe-Nt play a significant role on the change of metal centered (MC) ground states. With Fe-Nt extended by fluorine atoms, the quintet state becomes lower than the singlet state. Due to the deformation of structures, the interactions between metal and ligands diminish and give rise to weaker d orbital splitting than that of [Fe(tpy)2]2+, but slightly impact the pairwise orbital deformation density characteristics. And the PEC of 5MC intersects with 1,3MC which renders faster non-radiative deactivation through low-lying energy crossing points.

Stable phenalenyl (PLY) radical π-dimers still play an important role for new multifunctional materials owing to their intriguing molecular structure and unusual pancake π-π bonding mode. Herein, we design a new biphenalenyl biradicaloid (1) consisting of two PLYs and one benzene ring linkage tethered by single bonds, which presents an open-shell character. Further, three π-dimers (a1, b1, and c1) combined with 1 and conventional biphenalenyl biradicaloid (a, b, and c), which are capable of forming two staggered PLY dimers, exhibiting a short interlayer distance between the monomers. Interestingly, the analysis of the frontier molecular orbital reveals that two bonding orbitals, namely, the two highest occupied molecular orbitals (HOMO and HOMO-1) are doubly occupied. The results reveal that three π-dimers display two parallel pancake bonds. Moreover, they have small diradical and tetraradical characters, large interaction energies, and strong aromaticity, which indicate the stability of these π-dimers. The present work creates a new class of strong pancake bonding and might be utilized in devising an array of materials.

Besides the classic double bond scheme, several novel schemes have been proposed to describe the nature of the chemical bond in dicarbon, including a quadruple bond and a singlet diradical state. The results presented here show a harmony between MO and VB theories., Besides the classic double bond scheme, several novel schemes have been proposed to describe the nature of the chemical bond in dicarbon (C2), including a quadruple bond and a singlet diradical state. The results from a symmetry-broken CASSCF(8,8)/aug-cc-pVTZ study present a harmony between MO and VB theories, based on the orthogonal hybridization of the 3σg and 2σu orbitals together with the other six pristine valence orbitals. This scheme achieves the same bonding energy, RC–C, ωe and one electron density as that from the eight pristine valence orbitals. A quadruple bond scheme, identical to Prof. Shaik's result from VB theory, is achieved with the 4th bond energy in the range of 12.8–27.6 kcal mol–1. Meanwhile, the weight of a singlet open-shell configuration is the highest among all the possible configurations.

Two pillared-layer metal-organic frameworks (MOFs; PMOF-55 and NH2 -PMOF-55) based on 1,2,4-triazole and terephthalic acid (bdc)/NH2 -bdc ligands were assembled and display framework stabilities, to a certain degree, in both acid/alkaline solutions and toward water. They exhibit high CO2 uptakes and selective CO2 /N2 adsorption capacities, with CO2 /N2 selectivity in the range of 24-27, as calculated by the ideal adsorbed solution theory method. More remarkably, the site and interactions between the host network and the CO2 molecules were investigated by single-crystal X-ray diffraction, which showed that the main interaction between the CO2 molecules and PMOF-55 is due to multipoint supramolecular interactions of C-H⋅⋅⋅O, C⋅⋅⋅O, and O⋅⋅⋅O. Amino functional groups were shown to enhance the CO2 adsorption and identified as strong adsorption sites for CO2 by X-ray crystallography.

In 2003, a novel compound 2 containing the benzo-15-crown-5 moiety was synthesized and described. In the present work, we have designed two compounds 1 (benzo-12-crown-4) and 3 (benzo-18-crown-6) on the basis of compound 2. Further, nine configurations N*M (N = 1, 2 and 3; M = Li+, Na+ and K+) are designed by the compounds 1, 2 and 3 complexing alkali metal cations. Density functional calculation is performed to investigate the effect of ring size and the nature of the alkali metal cations on the interaction energy, charge transfer and nonlinear optical properties. The results indicate that the interaction energy of N*M depends on both the ring size and the nature of the alkali metal cations. Moreover, the amount of net charge transfer is related to the diameters of the alkali metal cations. In addition, the calculated nonlinear optical properties reveal that compound 2 has the largest first hyperpolarizability among the three compounds 1, 2 and 3. However, the alkali metal cations give rise to different effects on the nonlinear optical properties. Significantly, the order of the first hyperpolarizability can be explained by the transition energy and the dipole moment variation within the two-state approximation.

The photosensitive polyoxometalate (POM) [PW11O39RhCH2CO2H]5− was first introduced into the liquid crystal material through the encapsulation of dimethyldioctadecylammonium (DODA+). The theoretical calculation was performed to simulate the distribution of DODA+ around the POM anion. The surface photovoltage spectroscopy (SPS) result indicated that the hybrid exhibits the photovoltaic effect upon optical illumination and displays the character of a p-type material, which paves a new way for their potential application in the optoelectronics.

Carbon–boron–nitride heteronanotubes have attracted much interest owing to their adjustable properties and wide applications in many fields. In this work, the structures and first hyperpolarizabilities (β0) of a series of HA-n and isoelectronic PA-n heteronanotubes are investigated, in which HA-n is composed of a helical C segment and BN segment, and PA-n is composed of an arc C segment and BN segment. Interestingly, the helix C segment in HA-9 leads to a fascinating long-range charge-transfer character. As a result, the β0 value of HA-9 is 1.80×104 a.u., which is much larger than that of PA-9 (4.99×103 a.u.). Significantly, the β0 value of the C segment in HA-9 is 1.72×104 a.u., whereas that of the BN segment in HA-9 is much smaller (7.48×102 a.u.). In this context, the larger β0 value of HA-9 is essentially induced by the helix topological effect of the C segment. It is our expectation that this new knowledge about heteronanotubes might provide more ideas for further exploration of sp2-hybridized carbon segments with special topologies.

In this work, we add different strength of external electric field (Eext) along molecule axis (Z-axis) to investigate the electric field induced effect on HArF structure. The H-Ar bond is the shortest at Eext ¼ � 189 � 10 � 4 and the Ar-F bond show shortest value at Eext ¼ � 185 � 10 � 4 au. Furthermore, the wiberg bond index analyses show that with the variation of HArF structure, the covalent bond H-Ar shows downtrend (ranging from0.79 to 0.69) and ionic bond Ar-F shows uptrend (ranging from 0.04 to 0.17). Interestingly, the natural bond orbital analyses show that the charges of F atom range from � 0.961 to � 0.771 and the charges of H atoms range from 0.402 to 0.246. Due to weakened charge transfer, the first hyperpolarizability (btot) can be modulated from 4078 to 1087 au. On the other hand, make our results more useful to experimentalists, the frequency-dependent first hyperpolarizabilities were investigated by the coupled perturbed Hartree-Fork method. We hope that this work may offer a new idea for application of noble-gas hydrides. V C 2013 Wiley Periodicals, Inc.

Excess electron compounds have been proposed to be novel candidates of high-performance nonlinear optical (NLO) materials because of their large static first hyperpolarizabilities (β0). To enhance the stability of an unstable excess electron compound (LiCN⋯Li) with an extremely large β0 value (310196 a.u.), we designed a boron nitride nanotube (BNNT) as a protective shield molecule to encapsulate it (in theory). The stability of LiCN⋯Li was enhanced: the vertical ionization potentials (VIP) of LiCN⋯Li increased after encapsulating. Therefore, by comparison with LiCN⋯Li, the encapsulated complexes are more difficult to oxidize. Significantly, the BNNT encapsulated LiCN⋯Li complex exhibits a considerable β0 value (10645 a.u.), which is significantly (almost 380 times) larger than 28 a.u. of BNNT. Our further investigations into the intrinsic hyperpolarizabilites (βint) of these compounds show that there are clearly dependencies of the NLO response on the transition energy. Furthermore, it is easy to encapsulate LiCN⋯Li from the B-rich edge rather than N-rich edge of BNNT due to the lower energy barrier, which makes our calculations more useful to experimentalists who may try to synthesize these compounds. Knowledge of the encapsulation process of LiCN⋯Li within BNNT provides a new strategy for the design and synthesis of stable high-performance NLO materials.

A 3D pillar-layer framework (1) with uncoordinated carboxyl groups exhibits exceptional stability. It can effectively and selectively adsorb Cu(2+) ions and has been applied as a chromatographic column for separating Cu(2+)/Co(2+) ions.

The unusual properties of species with excess electrons have attracted a lot of interest in recent years due to their wide applications in many promising fields. In this work, we find that the excess electron could be effectively bound by the B atoms of boron nitride nanotube (BNNT), which is inverted pyramidally distributed from B-rich edge to N-rich edge. Further, Li@B-BNNT and Li@N-BNNT are designed by doping the Li atom to the two edges of BNNT, respectively. Because of the interaction between the Li atom and BNNT, the 2s valence electron of Li becomes a loosely bound excess electron. Interestingly, the distribution of the excess electron in Li@N-BNNT is more diffuse and pyramidal from B-rich edge to N-rich edge, which is fascinating compared with Li@B-BNNT. Correspondingly, the transition energy of Li@N-BNNT is 0.99 eV, which is obviously smaller than 2.65 eV of Li@B-BNNT. As a result, the first hyperpolarizability (3.40×10(4) a.u.) of Li@N-BNNT is dramatically larger (25 times) than 1.35×10(3) a.u. of Li@B-BNNT. Significantly, we find that the pyramidal distribution of the excess electron is the key factor to determine the first hyperpolarizability, which reveals useful information for scientists to develop new electro-optic applications of BNNTs.

On the basis of the famous staggered biphenalenyl diradical π dimer 1, the eclipsed biphenalenyl (1 a), with no centrosymmetry, was obtained by rotating a layer of 1 by 60° around its central axis. Furthermore, the central carbon atoms of 1 and 1 a were substituted by boron and nitrogen atoms to form 2 and 2 a with a novel 2e–12c bond. We found that the novel 2e–12c bond is formed by the electron pair of the occupied orbital of the phenalenyl monomer substituted by the nitrogen atom and the unoccupied orbital of the phenalenyl monomer substituted by the boron atom. As a result of the novel 2e–12c bond, 2 and 2 a exhibit a fascinating interlayer charge-transfer transition character, which results in a significant difference in the dipole moments (Δμ) between the ground state and the crucial excited state. The values of Δμ for 2 and 2 a are 6.4315 and 6.9253 Debye, clearly larger than the values of 0 and 0.0015 Debye for 1 and 1 a. Significantly, the boron/nitrogen substitution effect can greatly enhance the first hyperpolarizabilities (β0) of 2 and 2 a with a novel 2e–12c bond compared with 1 and 1 a with a traditional 2e–12c bond: 0 and 19 a.u. for 1 and 1 a are much lower than 3516 and 12272 a.u. for 2 and 2 a. Furthermore, the interaction energies (Eint)of 2 and 2 a are larger than those of 1 and 1 a, which could be considered as a signature of reliability for the newly designed dimers. Our present work will be beneficial for further theoretical and experimental studies on the properties of molecules with the novel 2e–12c bond.

Two novel iridium(III) complexes (pbi)2Ir(mtpy) (1) and (pbi)2Ir(pbim) (2) adopting 1,2-diphenyl-1H-benzoimidazole (Hpbi) as cyclometalated ligands were successfully synthesized and characterized. Strong emissions at 501 and 536 nm with high photoluminescence quantum yields of 48% and 91% in CH2Cl2 at 298 K were obtained for 1 and 2, respectively. The quantum chemical calculations and the photophysical properties indicated that the dominant 3MLCT (metal-to-ligand charge-transfer) state mixed with 3LLCT (ligand-to-ligand charge-transfer) and 3LC (ligand-centered 3π–π*) characters contributed to their phosphorescence emissions. Doped organic light-emitting diodes (OLEDs) based on 1 and 2 showed a peak current efficiency of 45.0 cd A−1 and power efficiency of 47.9 lm W−1 accompanied by very low efficiency roll-off values. In their non-doped OLEDs, high efficiencies of 24.4 cd A−1 and 26.3 lm W−1 were achieved as well. These appealing results reveal that complexes 1 and 2 open interesting perspectives for the development of high-performance OLEDs in the future.

A novel iridium(III) (pbi)2Ir(biq) with a strong orange emission at 573 nm was synthesized, which showed a high photoluminescence quantum yield (PLQY) of 45% in CH2Cl2 at 298 K. The quantum chemical calculations together with the photophysical properties indicated that the transition incorporation of 3MLCT (metal-to-ligand charge transfer), 3LLCT (ligand-to-ligand charge transfer) mixed with 3LC (ligand-centered 3π–π*) characters contributed to the emission of (pbi)2Ir(biq). Cyclic voltammetry (CV), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were then performed to investigate its electrochemical and thermal properties for fabrication of electroluminescent devices. Interestingly, complex (pbi)2Ir(biq) exhibited wide-bandwidth in electroluminescence (EL) of its orange electroluminescent devices, which made it effectively available to fabricate high-quality two-element white organic light-emitting diodes (WOLEDs). The resultant WOLED possessed a high current efficiency (ηc) of 22.1 cd A−1 and power efficiency (ηp) of 25.5 lm W−1 with a high color rendering index (CRI) of 80. Especially, the WOLED retained a favorable ηp of 10.9 lm W−1 and ηc of 16 cd A−1 at a high luminance of 1000 cd m−2. Moreover, it was worthwhile to note that this WOLED exhibited a qualified R9 of 13 and Duv of −0.0013, and these values together with the high CRI conformed to the required standard for lamp illumination of the ENERGY STAR.

Recently, C60Cl8 (C2v) has been experimentally synthesized (Y.-Z. Tan, et al., Nat. Mater., 2008, 7, 790) by the addition of eight chlorine atoms to C60 (C2v), which is associated with a Stone–Wales transformation of C60 (Ih). In this work, the first hyperpolarizabilities (βtot) of C60 (C2v) and C60Cl8 (C2v) are investigated. After the Stone–Wales transformation and chlorine addition reaction, the βtot values slightly increase from 0 for C60 (Ih) to 60 au for C60 (C2v) and 502 au for C60Cl8 (C2v), respectively. To further enhance the first hyperpolarizability, the endohedral fullerene derivative, Li@C60Cl8, formed by encapsulating a lithium (Li) atom inside the C60Cl8, has been designed. Interestingly, the electron transfer between Li and C60Cl8 leads to an extremely large βtot value of 25 569 au, which is considerably larger (51 times) than the 502 au of C60Cl8. It shows that the encapsulated Li effect plays an important role in enhancing the first hyperpolarizability, so the Li@C60Cl8 can be considered as a candidate for high-performance nonlinear optical materials.

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.