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The nonlinear optical responses of carbon nanohoop derivatives increase significantly with the increasing number and the length of π-bridges.

To compare homoleptic [2]catenanes and single rings consisting of gold(i) thiolates, the geometric and electronic structures, absorption spectra, binding energy, interaction energy and composition of intramolecular forces were studied theoretically.

DFT and TD-DFT calculations were performed to turn conventional non-TADF units into high-lying reverse intersystem crossing D–A–D-type TADF emitters.

Two planar-like molecules, 1 and 2, were designed and characterized via the introduction of BNB or NBN bonds into the planar phenalenyl.

Spin-unrestricted DFT and spin-unrestricted TDDFT calculations were performed to systematically investigate the correlation between the electron donating ability of donors and photophysical properties in D–A luminescent radicals.

Objective To explore the effects and value of establishing a multi-target nursing group (MTNG) for facilitating goal-oriented enhanced recovery after surgery (ERAS) using the LEER (“less pain”, “early movement”, “early return to a normal diet” and “reassurance”) model. Methods The clinical data of 198 patients with hepatobiliary and pancreatic malignancies were retrospectively analyzed. The patients were divided into two groups: 91 cases were collected in a traditional group, which adopted traditional perioperative care, and 107 cases were collected in an MTNG group, which adopted MTNG measures. The differences in the clinical data including postoperative recovery, unplanned readmission rate, the implementation rate of nursing measures, the degree of a patient’s understanding of the disease, and patient compliance and satisfaction with nursing care during hospitalization were compared and analyzed between the two groups. Results The MTNG group reflected a lower pain degree and hospitalization expenses (P < 0.05), earlier postoperative flatulence, earlier recommencing of a normal diet, and earlier postoperative ambulation (P < 0.05), together with a shorter postoperative indwelling catheter duration and length of hospital stay (P < 0.05). There were no significant differences in the incidence of postoperative complications and unplanned postoperative readmission rates between the two groups (P > 0.05). The implementation rate of nursing measures and the degree of patients understanding the disease, and patient compliance and satisfaction with nursing care were higher in the MTNG group (P < 0.05). Conclusion The MTNG approach, based on ERAS with the LEER model, was conducive to the safe and rapid postoperative recovery of patients, the precise and efficient implementation of ERAS measures, the improvement of medical treatment satisfaction among patients.

The present work aims to study the effect of an external electric field as well as arrangement of donor–acceptor groups on the second-order nonlinear optical (NLO) properties of push–pull systems. The first hyperpolarizabilities (βtot) of acceptor–donor molecules (m-AD and p-AD regioisomers) are investigated based on 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) as the electron-acceptor and benzodithiophene (BDT) as the electron-donor. Calculated results show that the βtot value (7.49 × 103 a.u.) of p-AD is larger than that (1.03 × 103 a.u.) of m-AD. Furthermore, we investigate that the external electric fields (along the positive or the negative directions of x-axis, Fx and F−x) regulate the NLO properties of the p-AD. (1) As Fx increases, the βtot values of p-AD are gradually decreased to 0 (Fx ranging from 0 to 30 × 10−4 a.u.). (2) As F−x increases, the βtot values are sharply increased (F−x ranging from 0 to −30 × 10−4 a.u.). It is worth noting that the βtot value is increased to 3.70 × 104 a.u. (F−x = −30 × 10−4 a.u.). Moreover, the evolutions of the simulated UV-Vis absorption spectra can well explain the trends of βtot values under an external electric field. The present work not only provides a deeper understanding of the relationship between structure and NLO properties, but also expands electric field-induced switchable NLO materials.

Many interesting multifunctional materials are obtained under the application of an external electric field, which arouses extensive interest of experimental and theoretical researchers. In the pre...

Phenalenyl (PLY) and its derivatives could form one-dimensional π-aggregates through pancake π–π bonding, which would lead to exotic optoelectronic properties. We will highlight the key aspects of the PLY derivatives from the design strategies to exploration of the electronic properties. Here, we primarily construct alternating boron (B)- and nitrogen (N)-doped PLY π-aggregates: dimer[12], trimer[12-1], trimer[12-2], tetramer[12]2, pentamer[12]2-1, pentamer[12]2-2, and hexamer[12]3. The geometric and electronic structures show that the short intermolecular distances of the π-aggregates drive the formation of pancake π–π bonding. Significantly, the molecular structures show periodic changes in the π-aggregates, but the first hyperpolarizabilities (βtot) present unexpected changes, which are found to increase sharply with increasing even layer thickness due to intermolecular charge transfer. The βtot value of hexamer[12]3 (5.72 × 104 a.u.) is 6.4 times that of tetramer[12]2 (8.95 × 103 a.u.), and is 22.4 times that of dimer[12] (2.55 × 103 a.u.). Thus, constructing π-aggregates can significantly improve the second-order NLO response, which is mainly due to intermolecular charge transfer through pancake π–π bonding of the interlayers.

The nature of the 2e/12c bond and its conversion to a carbon-carbon single bond in phenalenyl dimers have prompted a great deal of interests recently. In this work, we theoretically investigated a series of π-stacking phenalenyl derivatives with 2e/12c bonding character by density functional theory (DFT) calculations to elucidate origin of this unusual bond conversion. Results show that bond-conversion of the phenalenyl dimer easily occurs at room-temperature both dynamically and thermodynamically. However, bond-conversion of hetero π-stacking adducts, in which the two center carbon atoms were substituted by boron and nitrogen atoms, respectively, is much more difficult, because the 2e/12c bond is stabilized by its charge transfer character. Consequently, the bond-conversion is an endothermic process, albeit with a low conversion barrier. Interestingly, Lewis acid-base interactions would be induced by substitution of the center nitrogen atom to phosphorus atom. The 2e/12c bond is further stabilized by 5.9 kcal mol-1 and its conversion is also thermodynamically unfavorable.

In this work, three complexes C59Co, C59Rh and C59Ir are devised by the transition metals (Co, Rh and Ir) doped into fullerenes to study the structure–property relationships of the heterofullerenes...

A tunable terahertz (THz) metasurface (MS) absorber based on the surface phonon polariton (SPhP) is proposed based on a layered structure that consists of a split-silver-ring array followed by a graphene layer, polar crystal layer, and silver layer. A dynamically tunable, polarization-independent, and angle-insensitive MS absorber is numerically investigated at THz frequencies. By changing the Fermi energy of graphene from 0 to 1.0 eV, the state of the absorber can switch between the OFF state (with an absorptivity above 90%) and ON state (with an absorptance below 3%). The switching intensity (SI) of the absorber remains greater than 80% for TE incidence wave with incident angles from 0° to 70° and for TM incidence wave incident angles from 0° to 40° in the frequency range from 2.74 to 3.51 THz. These results should be helpful in guiding the design of THz tunable devices such as optical switches, smart absorbers, and imaging.

An interesting biphenalenyl biradicaloid (IDPL) dimer consisting of both-middle superimposed phenalenyls and both-end nonsuperimposed phenalenyls has been synthesized, and has attracted intensive research interest due to its intra- and intermolecular interactions and semiconductive characteristics. It is significant that under regulation of the external electric field the directional charge transfer (CT) can produce attractive properties. In the present work, the structure and electronic properties of the IDPL dimer under an external electric field (along the horizontal Fx or the vertical Fz directions) are explored, and the following properties determined: (i) as the horizontal Fx increases, the intramolecular CT becomes larger, which induces the intermolecular CT of the IDPL dimer. (ii) In contrast, as the vertical Fz increases, the large intermolecular CT gives rise to the intramolecular CT of the IDPL dimer. (iii) More importantly, the external electric field effectively regulates and controls the first hyperpolarizability (βtot) of the IDPL dimer. Compared with the vertical Fz, the horizontal Fx induces a larger first hyperpolarizability (βtot = 5.48 × 105 a.u.). Furthermore, the application of a uniform external electric field (Fx,y,z) to the IDPL dimer was investigated to define the external electric field direction of the material application. The βtot values were increased with increasing of the uniform Fx,y,z. Our study provides an effective strategy for developing high-performance NLO materials by tuning the external electric field, and could be of significance for application in switch devices.

Based on s-indaceno[1,2,3-cd;5,6,7-c′d′]diphenalene (1) consisting of two phenalenyl moieties, the monomer 2 and its dimer 22 are designed by boron and nitrogen atoms substituting the central carbon atoms of phenalenyl moieties. Calculated energy decompose analysis (EDA) shows that the orbital interaction for 22 possesses a large attractive contribution of −18.31 kcal mol–1, which is dominated by the π–π stacking interaction between the upper and the lower π-conjugated units. Interestingly, the natural population analysis (NPA) charge and the transition density matrix (TDM) show that both intramolecular charge transfer and intermolecular charge transfer (CT) exist in 22. Further, the first hyperpolarizability (βtot = 4.56 × 104 au) of 2 with intramolecular CT is greatly larger than that of reported molecule 3 (5.45 × 103 au) with intermolecular CT. Significantly, 22 exhibits the largest βtot value to be 1.42 × 105 au, which is caused by combining the intra- and intermolecular CT transitions (βx = 1.40 × 1...

Recently, the structure-property relationships of an attractive isomeric radical 1 (Phys. Chem. Chem. Phys., 2016, 18, 29041–29044) with famous phenalenyl (PLY) was investigated. Can PLY and 1 form stable π-dimers? The single point energy scan result shows that the staggered π-dimer (2) has the lowest energy. In order to explore intermolecular charge-transfer and nonlinear optical property, two π-dimers (2a and 2b by boron and nitrogen atoms substituting the central carbon atoms of 2) are designed. 2 has smaller intermolecular charge-transfer (0.020) and the first hyperpolarizability (βtot, 3.18 × 102 au). However, boron and nitrogen substitution effect can greatly enhance intermolecular charge-transfer (0.215 for 2a and 0.181 for 2b) and the βtot values (6.32 × 103 for 2a and 6.80 × 103 for 2b). Interestingly, the βtot values of 2a and 2b are close to each other, but their βz components and the NBO charge analysis show that 2a and 2b have opposite direction of charge transfer, which can be well explained by the difference of the dipole moment component (Δμz) between the ground and the excited states. Further, the first hyperpolarizability density study clearly substantiates the difference in their βzzz values: negative contribution for 2a is much larger than positive contribution, while the first hyperpolarizability density for 2b shows much larger positive contribution. Thus, the primary component of βzzz is negative value for 2a and βzzz is positive value for 2b. Combining with the frontier molecular orbital (FMO) and the electron density difference map (EDDM), intermolecular charge-transfer transition from B substituted fragment to N substituted fragment for 2a and 2b is concluded. The significant structure-property relationships in present π-dimers are beneficial for further theoretical and experimental investigations of high-performance nonlinear optical materials.

Due to wide applications in optoelectronic field, carbon-boron-nitride materials have attracted considerable interest from scientists. In the present work, the structures and first hyperpolarizility (βtot) of three closed shell isoelectronic structures BNC-n (n = 1–3) were investigated, in which BNC-n are designed by the increasing vertical carbon-segment doping into the BN nanosheet. Results show the βtot value of isoelectronic are increased with the increase of the doping carbon-segment. Among these isoelectronic structures, the βtot value (2.80 × 104 au) of BNC-3 is larger (19 times) than the 1.51 × 103 au of BNC-1. Correspondingly, the BNC-3 has the smallest transition energy (1.455 eV), which is obviously smaller than 3.884 eV of BNC-1. We hope the present work is beneficial for scientists to understand and design high performance nonlinear optical materials on carbon-boron-nitride hetero-materials.

Phenalenyl π-dimer (PLY2) has recently attracted intensive research interest due to its unique structure and binding characteristics (two-electron/12-center bonding). The directional transfer of electron or electron pair under the external electric field can produce a new structure with interesting properties. In the present work, we investigate for the first time the effect of the external electric field along the main molecule axis on PLY2. Two unpaired electrons between two layers are gradually shifted to the upper layer with increasing of the external electric field strength (Fext): the weaker the two-electron/12-center bonding, the stronger the electrostatic interaction between two layers. Significantly, a small increment of Fext makes a big difference: the interlayer distance in the PLY2 is sharply elongated from 3.241 A (Fext = 203 × 10–4 au) to 3.485 A (Fext = 204 × 10–4 au), which leads to the two-electron/12-center bonding breaking at 204 × 10–4 au. Therefore, the Fext = 204 × 10–4 au is regarde...

Four novel luminescent metal-organic frameworks (F1, F2, F3, F4), containing cadmium ions, carboxylic acid ligands, and the anthracene nitrogen-containing organic ligand (9,10-bis(N-benzimidazolyl)-anthracene, L) were synthesized by a one-pot synthesis under solvothermal conditions. F2, F3, and F4 show porous three-dimensional (3D) structures and F1 is characterized by a 2-fold interpenetrating 3D structure. Fluorescence sensing experiments reveal that F2, F3, and F4 are cable of multifunctional chemosensors to detect picric acid (TNP), pesticides as well as ferric ions with high sensitivity, selectivity, and good recoverability. Furthermore, theoretical studies demonstrate that the quenching phenomenon may be well explained by the mechanism of competitive absorption of excitation energy, electron transfer as well as the resonance energy transfer.

A series of diradical π-dimers 2 with interesting pancake-shaped 2e/24c π-π bonding character were designed and investigated based on the famous phenalenyl (PLY) π-dimer with 2e/12c π-π bonding character. The position of stronger interaction between two layers of radicals was found by the Wiberg bond index (WBI) maximum component. Further, the different contributions of the interaction energy were analyzed quantitatively by energy decomposition analysis (EDA). Among these new diradical π-dimers, 2180 has the smallest layer distance and the largest interaction between two layers of radicals. The unusual PLY analogues can provide new insights into the unique features of two-electron/multicenter (2e/mc) π-π bonding.

Intramolecular charge transfer (CT) in push-pull systems plays an important role in enhancing nonlinear optical (NLO) response. The main purpose of this work is to explore the effect of straight Z and twisted E isomers on the second-order NLO properties, two types of push-pull systems (Z(E)-A and D-Z(E)-A) based on the triphenylamine are designed and investigated. Significantly, the first hyperpolarizability (βtot) results show that the βtot value of straight Z-A is larger than that of twisted E-A. It is noteworthy that Z conformation modified by acceptor units can effectively adjust the second-order NLO properties. Further, D-Z-A and D-E-A systems combining multiple donor and acceptor units exhibit large second-order NLO properties. Obviously, D3-Z-A3 shows the largest βtot values of 2.46 × 104 au. Moreover, the trend of the transition energy (ΔE) value is inconsistent with the trend of βtot value, which explains the variation tendency of the βtot value. The presented correlation between conformation and the second-order NLO properties can provide a simple predictive tool to design highly NLO material based on triphenylamine derivatives.

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.

Very recently, an unprecedented novel monometallic cluster of fullerenes entrapping a yttrium cyanide (YCN) cluster inside a popular C82 cage YCN@Cs(6)-C82 was synthesized and characterized. Inspired by this investigation, four non-IPR YCN@C1(17459)-C76, YCN@C2v(19138)-C76, YCN@C2(17646)-C76, and YCN@C1(17894)-C76 (1, 2, 3, and 4) containing a pair of adjacent pentagons are designed to explore the encapsulated molecular effect on their interaction energies and nonlinear optical properties. The interaction energy (E int) values of 1, 2, 3, and 4 are -481.35 (1), -477.91 (2), -482.04 (3), -482.69 (4) kcal mol(-1), respectively, which shows that the E int value of 4 is the largest. Furthermore, the electron-transfer is mainly from the YCN to C76 cage. When YCN is encapsulated into C76 cage, we can find that the α0 values of the four molecules are very close, ranging from 6.50 × 10(2) to 6.65 × 10(2) au. Significantly, the first hyperpolarizabilities are in relation to the encapsulated molecular: 1.63 × 10(3) (1) > 8.03 × 10(2) (2) > 7.76 × 10(2) (4) > 4.86 × 10(2) au (3), the results show that the βtot value of 1 is the largest. Besides this, the encapsulation of the YCN to C76 cage brings some distinctive changes in its UV-vis spectra along with its other electronic properties that might be used by the experimentalists to develop the potential nonlinear optical nanomaterials based on endohedral metallofullerenes.

Very recently, two new cage-like radicals (C59B and C59N) formed by a boron or nitrogen atom substituting one carbon atom of C60 were synthesized and characterized. In order to explore the structure-property relationships of combination the cage-like radical and alkali metal, the endohedral Li@C59B and Li@C59N are designed by lithium (Li) atom encapsulated into the cage-like radicals C59B and C59N. Further, the structures, natural bond orbital (NBO) charges, and nonlinear optical (NLO) responses of C59B, C59N, Li@C59B, and Li@C59N were investigated by quantum chemical method. Three density functional methods (BHandHLYP, CAM-B3LYP, and M05-2X) were employed to estimate their first hyperpolarizabilities (β tot) and obtained the same trend in the β tot value. The β tot values by BHandHLYP functional of the pure cage-like radicals C59B (1.30 × 10(3) au) and C59N (1.70 × 10(3) au) are close to each other. Interestingly, when one Li atom encapsulated into the electron-rich radical C59N, the β tot value of the Li@C59N increases to 2.46 × 10(3) au. However, when one Li atom encapsulated into the electron-deficient radical C59B, the β tot value of the Li@C59B sharply decreases to 1.54 × 10(2) au. The natural bond orbital analysis indicates that the encapsulated Li atom leads to an obvious charge transfer and valence electrons distribution plays a significant role in the β tot value. Further, frontier molecular orbital explains that the interesting charge transfer between the encapsulated Li atom and cage-like radicals (C59B and C59N) leads to differences in the β tot value. It is our expectation that this work will provide useful information for the design of high-performance NLO materials.

Recently, the crystal structures and electrochemical properties of the isomers (Sc2S "trapped" in C82) have been reported, in which the Sc2S is located inside the different positions of the C82 cage. In the present work, three isomers of endohedral metallofullerenes Sc2S@C3v(8)-C82 (A, B, and C) have been designed to explore the effect of the position of Sc2S on their interaction energies and nonlinear optical properties. Among three isomers, the Sc2S is located in different positions of the C82 cage: the angles of Sc-S-Sc in A, B, and C are 104.9, 114.8, and 115.7°, respectively. Furthermore, the analysis of natural bond orbital (NBO) charge indicates that the electron-transfer is from the Sc2S to the adjacent carbon atoms of the C82 cage. The interaction energy of B is the smallest among three isomers which is -226.2 kcal mol(-1). It was worth mentioning that their first hyperpolarizabilities (β tot) were studied, we found that their β tot values were related to the positions of Sc2S: C (2100) > B (1191) > A (947 au). We hope that the present work can provide a new strategy to promote the nonlinear optical properties of endohedral metallofullerenes by changing the positions of the encapsulated molecular. Graphical abstract Three isomers of endohedral metallofullerenes Sc2S@C3v(8)-C82 (A, B, and C) have been designed to explore the position effect of Sc2S on the interaction energies and nonlinear optical properties. Among three isomers, the Sc2S in B has the most stable position. Significantly, the first hyperpolarizability is related to the position of Sc2S inside the C82 cage, which provides a novel strategy to enhance the first hyperpolarizability by the Sc2S revolving inside the C82 cage.