NLO Response Research Articles

Crystal structure, Hirshfeld surface analysis and third-order nonlinear optical properties of supramolecular complexes of 18-crown-6 with 6-hydrazinonicotinichydrazide and p-phenylenediamine

The crystal structures of the host-guest supramolecular complexes [2(6-HPCH)2+.3(18C6)].4[ClO4¯].2(H2O) (I) and [(PDA)2+.2(18C6)].2[Cl¯].10(H2O) (II) (18C6 = 18-crown-6; 6HPCH = 6-hydrazinylpyridine-1-ium-3-carbohydrazinium; PDA = p-phenylenediaminium) were determined by single-crystal X-ray diffraction analysis. Supramolecular assembly is constructed by NH···O, OH···O and C-H···O interactions. Both crystallize in the monoclinic system with centrosymmetric space group P21/n. The vibrational patterns in FT–IR are used to identify the functional groups. Direct band gap energy estimated by diffuse reflectance spectrum are, 3.42 eV for (I) and 4.78 eV for (II). Molecular interactions are analyzed by Hirshfeld surfaces, derived from single-crystal XRD data. Fingerprint plots of Hirshfeld surfaces were used to locate and analyze the percentage of hydrogen bonding interactions. A z-scan study was used to determine the third-order NLO response.

Alkali-Metal-Free Coinage Metalides: Specific Pairing and Location of Doping Atoms Bring Forth High Stability and Considerable Nonlinear Optical Response

The possibility to design alkali-metal-free coinage metalides as alternative species to the unstable alkalides has been explored by constructing a series of M-1-M’ (M; M’ = Cu, Ag, and Au) based on the facially polarized all-cis 1,2,3,4,5,6-hexafluorocyclohexane (1) in this work. Under the joint action of inherent polarization of 1 and the electronegativity difference between M’ and M, the s electron of Cu/Ag atom can be ejected to the Au atom, forming the diffuse excess electron around the Au– anions in the Cu+-1-Au– and Ag+-1-Au– complexes. Hence, they can be regarded as the first examples of alkali-metal-free coinage metalides. These two compounds not only have higher stability (larger VIE and Ec values) than previously reported alkalides but also exhibit remarkably larger β0 values than the reported coinage metalides M+-1-Au– (M = Li, Na, and K), demonstrating their great potential to serve as new molecular materials with considerable NLO responses. Taking Cu+-1-Cu– and Cu+-1-Ag– as examples, it is proved that the rest of the M-1-M’ compounds can also be converted into coinage metalides under oriented external electric fields (OEEFs), which provides an approach to obtain novel NLO molecular switches. This work will pave the way to design stable NLO materials by using coinage metal atoms instead of alkali metals, which are more likely to be synthesized in the laboratory.

Cyano-rich donor-acceptor-donor-type NLOphores containing dialkylated triazene and aniline groups

Continuous progress on the synthesis of push-pull chromophores is related to their outstanding optoelectronic properties. Expanding scope is a challenge due to the instability of targets and long synthetic strategies. Herein, we report the synthesis of thirteen different triazene-substituted alkyne substrates using Sonogashira cross-coupling reactions. Although we have previously described successful syntheses of homoconjugated and π-conjugated push-pull systems starting from triazene-substituted terminal alkynes, symmetric and unsymmetric bis-triazenes that we reported in this study unexpectedly did not undergo [2 + 2] cycloaddition-retroelectrocyclizations (CA-RE) with well-known electron acceptors, TCNE and TCNQ. With the use of diethylaniline-substituted substrates in CA-RE, this issue was successfully circumvented. Two different groups of NLOphores were synthesized in very high yields via [2 + 2] CA-RE with TCNE (95–99%) and TCNQ (92–99%). All target NLOphores were investigated by UV/Vis spectroscopy, thermal gravimetric analysis, high-resolution mass spectrometry, theoretical studies, and EFISHG experiments. While different dialkyltriazene groups did not appear to have an important impact on ICT properties of the chromophores, modifications made in the electron withdrawing units significantly affected the ICT performance of the chromophores. Target push–pull-systems displayed λmax values for their CT bands ranging between 454 and 692 nm. The ICT properties of the chromophores were confirmed by computational studies (Time-dependent density functional theory (TD-DFT) studies, frontier orbital visualizations, electrostatic potential maps, and calculation of several parameters such as dipole moment, HOMO-LUMO gaps, electronegativity, global chemical hardness, and softness, average polarizability, first hyperpolarizability) as well as experimental UV/Vis studies. As computational studies indicate that synthesized chromophores are potential NLOphores, experimental NLO measurements were performed by the EFISHG technique. Target structures exhibited large NLO responses (μβ values ranging 850 × 10−48 esu to 6050 × 10−48 esu).

Experimental and Theoretical Evaluation of Four NLO‐Active Divalent Transition‐Metal Complexes Supported by an Enantiomerically Pure Tetradentate Schiff Base Ligand

AbstractThis paper reports on a series of five chiral Schiff base push‐pull compounds derived from enantiomerically pure (1R,2R)‐(−)‐1,2‐diaminocyclohexane. The NiII, CuII, ZnII and PdII complexes supported by a ferrocene‐containing unsymmetrically‐substituted N2O2 quadridentate Schiff base ligand were prepared via template reactions and isolated in 74–87 % yields. A combination of EA, IR, UV/vis and 1H/13C{1H} NMR spectroscopy, HRMS spectrometry, cyclic voltammetry and single‐crystal X‐ray analysis (for the proligand 2 and its NiII derivative 3), together with computational methods (DFT and TD‐DFT) was used to fully characterize and study the properties of all products. Both 2 and 3 crystallize in the orthorhombic non‐centrosymmetric space group P212121, with two (R,R)‐(−)‐chiral carbon atoms in their structure. Second‐order nonlinear polarizabilities β have been measured by using Harmonic Light Scattering at 1.91 μm, with the Pd(II) species showing the higher NLO response of 460×10−30 esu.

Novel endohedrally and exohedrally metals (Li, Na, and K, Ag) doped (15-crown-5) with remarkable electronic, static and dynamic NLO response

In this study, an intriguing class of new complexes, in which 15-crown-5 is encapsulated by the Ag metal and exohedrally doped with alkali metals (Li, Na and K) is being explored for its electronic and optical response using ωB97XD/LANL2DZ functional of DFT. The three new complexes are thermally stable as evident from their interaction energy calculations. The alkali metals render excess electrons to the system which significantly reduced the HOMO-LUMO gap of new systems as compared to the bare crown. The intramolecular interactions are being evaluated by NBO analysis which revealed the alkali metals as donor species and Ag metal as an accepting moiety. The transparency of complexes in deep-UV region and monotonically decreasing excitation energy are key factors in proving their utility in optoelectronics. The estimation of static and dynamic first and second order hyperpolarizabilities reveal the significantly pronounced results. The maximum static first and second order nonlinearity are calculated for Ag(CR)K which are β0 = 3.69 × 104 au and γ0 = 5.08 × 105 au, respectively. The exceptionally high dynamic second hyperpolarizability for electric-field induced SHG is estimated to be 1.31 × 1010 au. The overall detailed study proves these materials as powerful candidates for NLO materials.

NLO properties and electride characteristics of superalkalis doped all-cis-1,2,3,4,5,6-hexafluorocyclohexane complexes

The designing and synthesis of efficient NLO materials is the demand of the century because of their importance in the development of photo-electronic devices. Herein, we studied the geometric, electronic, and nonlinear properties of superalkalis doped all-cis-1,2,3,4,5,6-hexafluorocyclohexane, Janus type complexes. These complexes have an unprecedented involvement of respective superalkalis as source of excess electrons, which resulted in the enhancement of nonlinear optical properties and electride characteristics. The interaction energies (−13.57 to −16.54 kcal mol−1) indicated the physisorption of superalkalis on C6H6F6. NBO charge analysis is used to predict the charge transfer during the complexation. The highest NLO response (1.68 ×106 au) is observed for Na2F@C6F6H6 complex. The enhancement in second hyperpolarizability (γo) values is seen at various frequencies. Further, to obtain NLO response from an experimental point of view, hyper Rayleigh scattering (βHRS) is also investigated. These complexes, in addition to being a new entry into excess electron compounds, will pave the way for the designing and synthesis of additional NLO materials. The remarkable static first hyperpolarizability (βo) and second hyperpolarizability (γo) responses make them ideal for future NLO materials.

Luminescent 1,10-Phenanthroline β-Diketonate Europium Complexes with Large Second-Order Nonlinear Optical Properties.

Substitution of the diglyme ligand of [Eu(hfa)3(diglyme)] (where hfa is hexafluoroacetylacetonate) with a simple 1,10-phenanthroline leads to a six-fold increase of the product μβEFISH, as measured by the Electric-Field-Induced Second Harmonic generation (EFISH) technique. Similarly, [Eu(tta)3(1,10-phenanthroline)] (where Htta is 2-thenoyltrifluoroacetone) is characterized by a large second-order NLO response. Both 1,10-phenanthroline europium complexes have great potential as multifunctional materials for photonics.

Alkaline earthides based on 15-crown-5 ether with remarkable NLO response

Alkaline earthides based on 15-crown-5 ether with remarkable NLO response

Phototunable Absorption and Nonlinear Optical Properties of Thermally Stable Dihydroazulene-Vinylheptafulvene Photochrome Pair.

The UV–vis absorption characteristics and nonlinear optical properties of a series of substituted dihydroazulene (DHA)/vinylheptafulvene (VHF) photoswitches are investigated by applying quantum calculations. Introduction of substituents at the seven-membered ring resulted in significant changes in their absorption properties depending on the nature and position of the substituent. Electron-donating groups at positions 5, 6, 7, and 8 generally exhibited red shifts with respect to the parent compound. However, the steric effect at positions 8a and 4 is responsible for the loss of planarity and conjugation, which generally leads to blue shifts. In contrast, any electron-withdrawing group, particularly at positions 8a and 4, would cause a blue shift. The presence of bulky groups at position 8a results in a loss of planarity and, as a result, a decrease in electronic conjugation within the molecule, resulting in a blue shift in the maximum absorption. When it comes to halogens, the red shift is directly correlated to the nucleophilicity; the higher the nucleophilicity, the larger the red shift. Regarding hyperpolarizability, the charge separation induces higher hyperpolarizabilities for all substituted VHFs compared to the corresponding DHAs, resulting in a much higher NLO response. In addition, for all DHA and VHF, the highest values of hyperpolarizabilities are calculated for 6-substituted systems. Finally, the objective of this detailed theoretical investigation is to continue exploring the photophysical properties of DHA–VHF through structural modifications.

Assessment of alkali and alkaline earth metals doped cubanes as high-performance nonlinear optical materials by first-principles study

Novel organic materials have played a tremendous role in developing high-performance nonlinear optical materials. Herein, the geometric, electronic and nonlinear optical properties of designed alkali (Li, Na, and K) and alkaline earth metals (Be, Mg, and Ca) doped cubane (C 8 H 8 ) complexes have been explored by using density functional theory. Excess electrons generated by doping alkali/alkaline earth metals have significantly enhanced the NLO properties by reducing the crucial excitation energy of the cubane. The HOMO–LUMO energy gap of doped complexes is reduced up to 4.43 eV. It is revealed that the reduction in the HOMO–LUMO energy gap results from the development of the new highest occupied molecular orbital, which is confirmed by the density of state (DOS) analysis. The NBO analysis is carried out to confirm the charge transfer between metal atoms and the cubane ring. Further, the NCI and QTAIM analyses confirmed the nature of intramolecular interaction. The remarkable first hyperpolarizability ( β o ) of 3.01 × 10 4 au is observed for K@Cubane. Moreover, frequency dependent first hyperpolarizability ( β ( ω )), second harmonic generation β (-2 ω ; ω , ω ), electro-optic Pockel's effect β (- ω ; ω ,0), hyper-Rayleigh scattering coefficient ( β HRS ), second hyperpolarizability ( γ ( ω )), electric field-induced second harmonic generation γ (-2 ω ; ω , ω ,0) electro-optic Kerr effect γ (- ω ; ω ,0,0), and nonlinear refractive indices ( n 2 ) were also studied. The highest dc-Kerr (2.69 × 10 10 au ) and EFISHG (3.69 × 10 9 au ) values observed for K@Cubane along with large n 2 (1.73 × 10 −9 au ) justify the large NLO response. These intriguing outcomes will be advantageous for promoting the possible utilization of designed complexes in the field of high-performance NLO materials. • Alkali and alkaline earth metals doped cubane complexes have been investigated theoretically for better NLO response. • NBO analysis indicates the intermolecular charge transfer while NCI and QTAIM analyses validate non-covalent interactions. • All the doped complexes have deep ultraviolet transparency (≤200 nm). • First hyperpolarizability ( β o ) of doped cubane complexes have been enhanced to 3.01 × 10 4 au. • Hyper-Rayleigh scattering (upto 2.23×10 4 au ) and nonlinear refractive index (upto 1.15×10 −5 au ) reflect high NLO response.

Second Harmonic Generation Behavior of Two New d-Ribose/d-Fructose and Metal Halogenide-Based Coordination Compounds and Comparison to d-Fructose and d-Galactose Analogues: An Experimental and Theoretical Approach

This work is focused on the understanding of the second harmonic generation (SHG) behavior of metal halogenides–saccharide-based compounds. Three new compounds were added to a list of such compounds that were previously analyzed by our group in order to deepen the understanding of the relationship between the SHG behavior of these materials and their structural and/or chemical properties. These new compounds were the object of theoretical calculations with two different computational approaches (nanoparticle and bulk) and were characterized by single-crystal X-ray diffraction (XRD), and SHG measurements were performed. The results demonstrate that DFT simulations can be considered as reliable predictors of the order of magnitude of the experimental measures. The nanoparticle calculations take into account the finite size of the crystals in the powders and the lowering of symmetry due to their defects. A multivariate analysis is performed to elucidate the relationship between the structural, chemical, and physical parameters and the NLO response.

Theoretical study on photophysical properties of twisted D-A interaction TPA-BSM derivatives

Luminogens with aggregation-induced emission (AIE) properties have received considerable attention as excellent candidates for optoelectronics, chemical/biosensors, and bioimaging. Recently, molecule TPA-BSM with the twisted intramolecular charge transfer, with a twist angle of 40.96° between the donor TPA and acceptor BSM units, has exhibited unique photophysical properties, especially the AIE properties in the aggregate and solid state. However, the relationship between their structure and performance has not been fully explored, which will further expand their application areas. Herein, based on the reported TPA-BSM, four new derivatives are designed. Their electronic structure, electron absorption, hole reorganization energy and second-order NLO response have been systematically studied using DFT and TD-DFT theories. It is found that they are all narrow bandgap derivatives. The introduction of donor units can reduce the energy gap, red-shift the first absorption peak, increase the dipole moment and the static first hyperpolarizability, while the introduction of acceptor units is just the opposite. However, the introduction of donor or acceptor units cannot further enhance the hole transport performance, but except for molecule TB-N(CH3)2, the other four derivatives are potential hole transport materials. Due to have large first hyperpolarizabilities of the investigated derivatives, they are promising candidates for excellent second-order NLO materials.

Synthetic approach to achieve halo imine units: Solid-state assembly, DFT based electronic and non linear optical behavior

Herein, two crystalline schiff bases: (E)-2,4-dibromo-6-(((3,4-dichlorophenyl)imino)methyl)phenol (DCBA) and (E)-2,4-dichloro-6-(((2,4,5-trichlorophenyl)imino)methyl)phenol(TCCA) were prepared by treating halo-substituted benzaldehydes with chloro-substituted aniline through condensation reaction. The crystal structures of DCBA and TCCA were confirmed by SC-XRD analysis, which unambiguously revealed that C-H···Br, C-Cl···π, and off-set π···π stacking interactions were the key aspects of crystal packing of DCBA, whereas π···π off-set stacking interactions were the main aspect ofcrystal packing of TCCA. Hirshfeld surface analysis had been implemented for the further probe of intermolecular interactions. Accompanying with experimental, DFT investigation had also been performed at M06/6-311G(d,p) level to analyze these crystalline architectures. By comparative analysis of geometrical parameters, an efficient agreement was observed between DFT and SC-XRD data. Additionally, natural bond orbital (NBO) findings revealed that most dominant hyper-conjugative transitions with higher stability (31.06 and 30.70 kcal/mol) had been examined for DCBA and TCCA, respectively, which may cause the stability of these molecules. Further, global reactivity parameters disclosed that both compounds showed larger value of hardness (η = 2.181–2.205 eV) with least value of softness (σ = 0.226–0.229 eV) which indicated them kinetically enormous stable and show excellent concurrence with NBO and SC-XRD. The band gaps of DCBA and TCCA had been rationalized to be 4.40 and 4.36 eV, respectively. Interestingly, significant values of dipole moment [µtotal = 1.03 and 4.16 a.u.], linear polarizability [<α>=309 and 1167.51 a.u.] and second order hyperpolarizability [<γ> =3.90–4.18 × 105a.u.] were investigated in the entitled compounds. Remarkable NLO response of aforesaid compounds designated them as outstanding NLO materials for the hi-tech optoelectronic applications.

Superhalogen doping of aromatic heterocycles; effective approach for the enhancement of static and dynamic NLO response

In this study, for the first time, static and dynamic NLO responses of pure and superhalogen doped aromatic heterocyclic monomers have been investigated by using density functional theory (DFT) calculations. The thermal, electronic, linear, and nonlinear optical properties are computed at the ωB97XD/6-31+G(d,p) method. The thermodynamic stabilities of reported complexes are estimated based on interaction energies, which are in the range of −28.06 to −83.20 kcal/mol. The lowest interaction energies are observed for AlF4@X (X = C4H4NH, C4H4O, C4H4S, and C5H5N) complexes, which correspond to their higher stabilities. The appreciable decrease in the HOMO-LUMO energy gap (Egap) is an indicative of the increase in reactivity after doping with superhalogens. The decrease in Egap is further demonstrated with the help of density of state (DOS) analysis. The significant nonlinear optical responses of the superhalogen doped aromatic heterocyclic monomers are due to the strong electron-withdrawing nature of the fluorine atom. Overall, the results indicate the high NLO response for the AlF4@X complexes due to the presence of four electron-withdrawing fluorine atoms in AlF4. The NLO results are further analyzed through the two-level model.

Optical and electrical properties of new NLO active ethynylated chalcone as solution-processed OLEDs material: Experimental and theoretical approaches

This present study investigated the contribution of new hybrid moieties of ethynylated (C≡C) and chalcone (–CO–CHCH-) units as nonlinear optically active and successfully applied to solution-processed OLEDs material. The simulated data from Density Functional Theory (DFT) indicates that 3-(pyren-1-yl)-1-((4-phenylethylyn)phenyl)-2-propen-1-one (MM-1a) reveals good polarizability properties of total first hyperpolarizability βtot at 842.32 × 10−30 esu associated with low HOMO-LUMO gap at 3.04 eV. The structure-property relationship also was highlighted using TD-DFT calculations for frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) maps and global chemical reactivity descriptors (GCRD). The photophysical behaviours of MM-1a presented emission maxima at 520 nm with large Stokes shifts at 95 nm where this emission shows fluoresce characters and intramolecular charge transfer (ICT) state. Remarkably, a response from the open and closed aperture Z-scan analysis reveals that MM-1a displays reverse saturable absorption (RSA) performance and self-defocusing effects under 532 nm continuous wave (CW) laser. Further, solution-processed OLED featuring single-layer of ITO/PEDOT:PSS/MM-1a/Au displayed electroluminescence effect by intense yellow emission obtained under direct current (DC) voltages supply. From the obtained result, the introduction of ethynyl as spacer in chalcone system facilitated intramolecular charge transfer and finely tuned the electronic properties to enhance NLO response and promising emissive layer for OLED applications.

Exploration of nonlinear optical enhancement and interesting optical behavior with pyrene moiety as the conjugated donor and efficient modification in acceptor moieties

Herein, a series of new pyrene based hexylcyanoacetate derivatives (HPPC1–HPPC8) with A–π–D–π–D configuration were designed by end-capped modeling of non-fullerene acceptors on the structure of reference compound named dihexyl 3,3'-(pyrene-1,6-diylbis(4,1-phenylene))(2E,2'E)-bis(2-cyanoacrylate) HPPCR. Quantum chemical calculations of HPPCR and HPPC1–HPPC8 were accomplished at M06/6-31G(d, p) level. The stability of molecules due to the strongest hyper conjugative interactions in HPPCR and HPPC1–HPPC8 was estimated through NBO study. Interestingly, HOMO–LUMO band-gap of HPPC1–HPPC8 was found smaller than HPPCR which resulted in large NLO response. Among all the investigated compounds, HPPC7 showed the larger NLO response due to the presence of four cyanide (CN) groups which strengthens the bridge conjugation, and its band gap was found to be 2.11 eV, smaller as compared to band gap of HPPCR (3.225 eV). The absorption spectra of HPPC1–HPPC8 compounds showed maximum absorption wavelengths (483–707 nm) than HPPCR (471.764 nm). The designed compounds showed high NLO response than HPPCR. Amazingly, highest amplitude of linear polarizability < α > , first hyperpolarizability (βtotal) and second hyperpolarizability < γ > for HPPC7 were achieved to be 1331.191, 200,112.2 and 4.131 × 107 (a.u), respectively. NLO response showed that the HPPC1–HPPC8 might be potential candidates for NLO applications.Graphical abstract

Nonlinear optical response of 9,10-bis(phenylethynyl)anthracene mediated by electron donating and electron withdrawing substituents: A density functional theory approach

Herein, we report linear polarizibilty (α) and hyperpolarizibility (β) of anthracyl-based organic materials containing electron acceptor (NO2) and electron donor (NH2) moieties. Six compounds (a–f) were designed by structural modification of a reported chromophore 9,10-bis(phenylethynyl)anthracene (R). Ground state geometries, HOMO-LUMO energies polarizability, first hyperpolarizability and natural bond orbital (NBO) analyses of all compounds (R and a–f) were studied through density functional theory. FMO's results showed that the energy gaps of designed molecules a–f (1.791–2.215eV) were much lower than parent molecule R (2.606 eV). UV Visible analysis of designed compounds showed a red shift in the absorption spectrum as compared with reference molecule (R). The highest λmax was observed for compound c (816.7 nm). NLO analysis and hyper polarizibility values computed for compounds a-f were much higher than reference compound R (0.023 a.u.). The observed red shifts in the absorption spectra indicated the decrease in excitation energy, an important factor in enhancing NLO response. Overall, compound c showed larger αtotal and βtotal values of 575.9 a.u. (LC-BLYP/6–31++G(d,p), and 58156.8 a.u. (LC-BLYP/6–31++G(d,p), respectively. The findings of our study provide a theoretical platform for useful conversion of centrosymmetric compounds to non-centrosymmetric materials for enhancing the NLO behavior through structural modifications for modern technological applications.

Third order NLO and second hyperpolarizability of functional porphyrin based polyimides

Porphyrin-POM hybrid materials with excellent NLO properties are supposed to be a worthy entrant for forthcoming telecommunication, optical fibers, optical data storage and optical limiting devices, but due to adverse solubility problems, they are replaced by polymeric materials. Herein, we assessed third order NLO and second hyperpolarizability of porphyrin-polyimide compounds (NH-PI and Zn-PI) synthesized from the reaction of 4,4ʹ-hexafluoroisopropylidene-diphthalic anhydride (6FDA) with C44H32N6 (NH-DATPP) and C44H30N4Zn (Zn-DATPP) porphyrins under ambient conditions. The Z-scan measurement of these compounds revealed reverse saturation absorption as well as self-defocusing performance. Zn-PI showed an enhancement in γ value (2.214 × 10−29 esu) as compared to the NH-PI (1.879 × 10−29 esu) revealing significant role of Zn ion in charge transfer process. On the other hand, Zn-DATPP exhibited χ(3) value of 7.829 × 10−11 esu which is significantly lower than the value seen for the compound NH-DATPP (15.649 × 10−11 esu) showing inverse effect due to ruffled deformation in normal coordination structure of metalloporphyrin. Furthermore, this work provides a pave to modulate the NLO response by fine structural modification in porphyrin-polyimides.

Experimental analysis of excited state dynamics in Anderson-type POM@porphyrin hybrids in relevance to third-order nonlinear optical properties

This work accounts for the active contribution of life time decay in the field of nonlinear optics, especially for an energetic donor acceptor couple (porphyrin and polyoxometalate (POM)). Currently, two POM free porphyrins (Di-Tris-N@Por and Di-Tris@Por) and their two hybrids with POM (Di-Tris-NPor@Di-AndPOM-1 and Di-TrisPor@Di-AndPOM-2) have been studied keenly in nanosecond time span and resulted lifetimes ([Formula: see text]1 and [Formula: see text]2) have been compared with nonlinear optical parameters. The results demonstrated that Di-Tris-NPor@Di-AndPOM-1 exhibited better third-order nonlinear optical susceptibility [Formula: see text]3, second hyperpolarizability [Formula: see text] and nonlinear absorption [Formula: see text] and Di-TrisPor@Di-AndPOM-2 than Di-TrisPor@Di-AndPOM-2. This superiority of nonlinear optical parameters was supported by lifetime decay studies and electrochemical studies. It is revealed that more relaxation time in excited states lower will be the NLO response. The lifetime decay ([Formula: see text]1) value of Di-Tris-NPor@Di-AndPOM-1 is 3.86ns which is higher than Di-TrisPor@Di-AndPOM-2 possessing lifetime decay ([Formula: see text]1) value of 2.45ns. Moreover, lower energy of charge separated state (-0.88 eV) of Di-Tris-NPor@Di-AndPOM-1 indicates the facile electron transfer in Di-Tris-NPor@Di-AndPOM-1 than Di-TrisPor@Di-AndPOM-2 which experienced more energy of charge separated state. Rapid intersystem crossing is also responsible for the electron transfer from porphyrin moiety to POM moiety.

Constructing a simple Cone–Chain motif to significantly enhance the first hyperpolarizability of horn-shaped carbon nanocones

According to the density functional theory (DFT) calculations, the first hyperpolarizabilities of the carbon nanocone (CNC)–based systems in a D–π–A framework can be prominently improved by constructing the mixed π-conjugated bridge. The hybrid π-conjugated bridge is constructed by modifying the bottom edge of CNC with –(CH CH) x –NH 2 /NO 2 chain. By connecting the –(CH CH) x –NH 2 chain with electron-donating characteristic, the first hyperpolarizabilities of these cone-chain systems can be enhanced more availably, and the substitution position can also play an important role in determining the β 0 value. The TDDFT calculations show that building the simple cone-chain motif can effectively improve the degree of charge transfer and reduce the transition energy, thus leading to a considerably large first hyperpolarizability, which is much larger than that of the corresponding directly NH 2 -decorated CNC system with the same conjugated length. Especially, the first hyperpolarizabilities of these cone-chain motifs (CNC–(CH CH) x –NH 2 ) can increase dramatically with the extension of –(CH CH) x –NH 2 chain. Furthermore, in view of the unique horn-shaped structure of CNC, another –(CH CH) x –NH 2 chain is added at the bottom edge for double-substitution, and it can further augment the first hyperpolarizability compared with the single-substitution. In addition, the length ratio of cone to chain in the mixed π-conjugate bridge can also have a crucial effect on the β 0 value of these cone-chain motifs. Using the –(CH CH) x –NH 2 with a comparable conjugated size to modify the bottom edge of cone can be an effective strategy for achieving the remarkable NLO response in the CNC-based system with D–π–A framework. These fascinating findings are advantageous for the design of new high-performance NLO materials based on CNCs. Constructing a simple cone–chain motif can be considered as a new and effective strategy to significantly increase the first hyperpolarizability of carbon nanocones (CNCs), which can be mainly attributed to the fact that when linking the π-conjugated –(CH CH) x –NH 2 /NO 2 chain with electron-donating/withdrawing characteristic, the abundant π electrons of CNCs can be well directed to result in the more effective charge transfer, just like inserting a straw into a glass of water, it allows the water to flow out more directionally. • Constructing a simple cone–chain motif can significantly increase the first hyperpolarizability of carbon nanocones (CNCs). • The β 0 value of CNC can be enhanced more effectively by linking electron-donating -CH=CH–NH 2 chain. • When elongating the chain length, a monotonous increasing trend can be observed for the β 0 value. • The double-chain substitution of –(CH=CH) x –NH 2 can further enhance the β 0 value of CNC system. • The β 0 value of CNC l –(CH=CH) x –NH 2 can be adjusted effectively by changing the length ratio of cone to chain.