Order NLO Response Research Articles

Investigation on Physicochemical Properties of Nonlinear Optical (NLO) Single Crystal: Rubidium Hydrogen Fumarate

A solvent evaporation method produced an optically high-quality semiorganic single crystal of Rubidium hydrogen fumarate (RbHF) at room temperature. The structural analysis reported that the RbHF crystallized in triclinic crystal system with centrosymmetric space group P1¯. The Powder XRD pattern indicates the grown crystal have good crystalline nature. FTIR spectroscopy examined the functional group and bonding in the grown molecule. A optical transparency of about 88% were observed in RbHF and having energy bandgap of 3.9 eV were calculated using Tauc’s plot. The grown crystals were thermally stable upto 170°C. Mechanical and dielectric analysis has been carried and their properties were discussed in detail. Intermolecular interactions were studied using Hirshfeld surface maps and 2D fingerprint plots. The grown crystal have positive photoconductivity nature. A Z-scan were used to study the third order NLO response in RbHF crystal. The third order nonlinear susceptibility of RbHF crystal was estimated as (χ3) = 1.60244 × 10-08 esu, nonlinear absorption coefficient (β) = 6.39395 × 10-5 cm2/W and nonlinear refractive index (n2) = 9.15822 × 10-12 cm/W. The observed results of the RbHF single crystal show, it has the potential application in optical and optoelectronic devices.

First, second and third order NLO response of alkaline earth metals doped C6O6Li6 organometallic complexes

The geometric, electronic, linear and nonlinear (NLO) properties of pure C6O6Li6 and alkaline earth metals (AEM) doped C6O6Li6 organometallics are studied through quantum chemical methods. Interaction (Eint) and vertical ionization energies illustrate the thermodynamic and electronic stabilities of considered AEM@C6O6Li6 organometallic complexes, respectively. The highest interaction energy value is noticed for Ca@C6O6Li6 complex (–22.78 kcal/mol). After doping of alkaline earth metals, HOMO-LUMO energy gap (H-L Egap) is remarkably reduced. The variation in H-L Egap indicates the conductive properties of these complexes which occur due to transfer of electrons from the alkaline earth metals to the C6O6Li6 surface or vice versa. The electronic density shifting is also supported by natural bond orbital (NBO) charge and molecular orbitals analyses. UV–VIS analysis is used to confirm the electronic excitations. These organometallics show deep ultra-violet transparency below 200 nm which justifies their application in future laser devices. A noticeable NLO response is observed for these organometallics which is confirmed from the static first order hyperpolarizability (up to 1.90 × 104 au) and second order hyperpolarizability (up to 7.11 × 106 au) along with higher refractive index (up to 1.68 × 10−12 au) at 532 nm. The hyperpolarizability values are further enhanced at dynamic frequencies and these are increased up to 5.82 × 1010 au. These results illustrate the use of these organometallics in optical technologies for achieving better dc-Kerr effect and second harmonic generation effects.

Linear and nonlinear optical properties of 2-Aminopyridinium fumarate fumaric acid single crystal for optoelectronic device applications

A good organic nonlinear optical single crystal of 2-Aminopyridine fumarate fumaric acid has been grown by slow evaporation technique. The analysis of single-crystal XRD demonstrates the centrosymmetric character of the grown crystal. The different functional groups and chemical composition are of 2APFF compounds were identified by using Fourier transform infrared spectral study. Spectral range of UV–vis-NIR studies shown that the transparency and band gap energy Eg = 6 eV of the grown crystal. Thermal property of 2APFF was analysed by differential scanning calorimetric technique. The mechanical properties 2APFF crystal was calculated for various load using the Vickers micro hardness tester. The dielectric behaviour of the grown crystal was studied for different temperatures at different frequencies. The third order NLO response in 2APFF was investigated using a Z-scan apparatus.

Inorganic electrides of alkali metal doped Zn12O12 nanocage with excellent nonlinear optical response

Finding new materials with exceptionally large nonlinear optical response is an interesting and challenging avenue for scientific research. Here, we report the alkali metal doped Zn12O12 nanocages as inorganic electrides with excellent nonlinear optical response. Density functional theory calculations have been performed for geometric, electronic and nonlinear optical response of exo- and endohedrally alkali metal doped Zn12O12 nanoclusters. For exohedral doping, all different possible doping sites are considered for decoration of alkali metal on the nanocage. The electride nature of the complexes is highly dependent on the position of alkali metal doping. All exohedral complexes except for alkali metal doping on six membered ring (r6) are electride in nature, as revealed from frontier molecular orbital analysis. Interaction energies reveal that all doped nanoclusters except endo-K@Zn12O12 are thermodynamically stable. The exothermic encapsulation of alkali metals in Zn12O12 nanocages is in marked contradiction with other inorganic fullerenes where encapsulation is an endothermic process. The barriers for boundary crossing are also evaluated in order study the interconversion of exo- and endohedral complexes. Doping of alkali metal significantly influences the properties of nanocages. HOMO-LUMO (H-L) gap is reduced significantly whereas hyperpolarizability is increased several orders of magnitude. The NLO response of exohedrally doped complexes is higher than the corresponding endohedral complexes, which is in mark contradiction with the behavior of phosphide or nitride nanocages. The highest first hyperpolarizability of 1.0 × 105 au is calculated for K@r6-Zn12O12 complex. Third order NLO response of these complexes is calculated and compared with the best systems reported in the literature at the same level of theory.

Crystal growth and characterization of 4-[4-(4-dimethylamino-phenyl) buta-1,3-dienyl]-1-methyl pyridinium iodide for higher order non-linear applications

We have developed a organic salt; 4-[4-(4-dimethylamino-phenyl) buta-1,3-dienyl]-1-methyl pyridinium iodide (DACSI) with extended π-conjugated system. DACSI single crystals have been grown by slow evaporation technique. The crystal structure of DACSI single crystal is determined using single crystal X-ray diffraction method. By employing the density functional theory, the molecular structure of DACSI is compared with the well known stilbazolium cationic choromophore; 4-N, N-dimethylamino-4′-N′-methylstilbazolium iodide. The study confirms that the extended π-conjugated system increased the planarity of DACSI when compared to DASI. Proton NMR analysis ascertained the existence of π-conjugated bridge between the 4-N, N-dimethylamino cinnamaldehyde and aromatic pyridinium structure. Infrared spectroscopy confirmed the vibrational modes of the vinyl, phenyl, and methyl and pyridinium structure of DACSI. The mechanical and dielectric characters of the compound are examined. The non linear optical parameters involving the first order hyperpolarizability (β), mean polarizability (αtotal) and NLO response of DACSI are computed and compared with DASI. Third order nonlinear optical properties are analyzed using the z-scan experimental data.

Syntheses, characterizations, crystal structures and efficient NLO applications of new organic compounds bearing 2-methoxy-4-nitrobenzeneamine moiety and copper (II) complex of (E)-N'-(3, 5-dichloro-2-hydroxybenzylidene) benzohydrazide

In the present study, we use a dual approach comprising of experimental and computational techniques to report the syntheses, characterizations (1H NMR, 13C NMR, FT-IR, UV–visible spectroscopy and X-ray structure determination) and theoretically evaluated the third order NLO response properties of the new organic compounds; 1-((E)-(2-methoxy-4-nitrophenylimino)methyl)naphthalen-2-ol hydrate (HL1), (E)-N-(ethoxy(2,3-dichlorophenyl)methyl))-2-methoxy-4-nitrobenzenamine(L2) and copper(II) complex [Cu(L3)(py)] of (E)-N'-(3,5-dichloro-2-hydroxybenzylidene)benzohydrazide(H2L3). The HL1 and L2 were crystallized in the triclinic system of the space group P-1 with two molecules in the unit cell, whereas complex [Cu(L3)(py)] was crystallized in the monoclinic system in the space groups P21/c with eight molecules in the unit cell. The thermal properties (DSC and TG-DTG analysis) of these compounds were also investigated. State of the art quantum computational methods are performed at molecular and bulk levels to get structure-property relationships from molecule to materials. For HL1, L2 and complex [Cu(L3)(py)], their isotropic (anisotropic) values are found to be 55.46 × 10−24 esu (71.69 × 10−24 esu), 44.67 × 10−24 esu (26.92 × 10−24 esu) and 60.73 × 10−24 esu (69.71 × 10−24 esu), respectively. The differences in isotropic and anisotropic values are 16.23 × 10−24 esu, 17.75 × 10−24 esu and 9.00 × 10−24 esu, respectively. The NLO response properties including third-order polarizability (γ) are calculated using density functional theory (DFT) methods. The calculated γ amplitudes for the synthesized HL1, L2 and complex [Cu(L3)(py)] are found to be 801.54 × 10−36, 77.81 × 10−36 and 311.17 × 10−36 esu, respectively. These γ amplitudes of HL1, L2 and complex [Cu(L3)(py)] are about 44, 4 and 17 times larger than that of standard para-nitroaniline (PNA, a prototype NLO molecule), respectively, which show the potential of these compounds as efficient NLO materials. Their electronic parameters and NLO properties were also evaluated using TD-DFT calculations. The HL1, L2 and complex [Cu(L3)(py)] showed maximum absorptions with oscillator strengths of 0.749, 0.393 and 0.368 at 2.751 3.476 and 3.214 eV, respectively.

Functionalized organic frameworks explored as second order NLO agents

A new class of chiral phthalimides functionalized with aryl piperazines was designed anticipating their strong candidature for crystal engineering and technological applications. Five new phthalimides were synthesized, characterized and subjected to single crystal X-ray diffraction study that directed their non-centrosymmetric structures. Four phthalimides crystallized in P21 space group with monoclinic crystal system, however, one was found to possess P212121 space group with orthorhombic system. The supramolecular architectures of phthalimide crystals were analysed by an approach based on consideration of energy of intermolecular interaction. The molecular hyperpolarizability (β) calculation for all the listed phthalimides indicated their promising candidature for NLO materials. Further, the crystalline form of all phthalimides was evaluated for their second harmonic generation (SHG) response. A significant response of 16.4 mV was measured for phthalimide possessing t-butyl substituent at the para position of 4-benzylpiperazine. This high SHG response may be attributed to the molecular chirality and helical supramolecular frameworks stabilized by C-H ⋯O hydrogen bonds in the solid state. The current study attests chiral phthalimides possessing arylpiperazines as effective nominees to the area of crystal engineering and nonlinear optics. New chiral phthalimides possessing terminal arylpiperazines have been studied for their solid-state properties. The second order NLO response of all the listed phthalimides was substantiated with the aid of computational study and crystal engineering approach.

Novel ruthenium(ii) complexes with substituted 1,10-phenanthroline or 4,5-diazafluorene linked to a fullerene as highly active second order NLO chromophores

Various Ru(II) complexes with substituted 1,10-phenanthroline or 4,5-diazafluorene are characterized by a good to very large second order NLO response, as determined by EFISH. Among these complexes, [Ru(9-fulleriden-4,5-diazafluorene)(PPh(3))(2)Cl(2)] is particularly appealing due to its huge second-order NLO response and its transparency to the second harmonic generation. The structure of cis-Cl,trans-PPh(3)-[Ru(5-NO(2)-1,10-phen)(PPh(3))(2)Cl(2))] was determined by single-crystal X-ray diffraction.

An EFISH, Theoretical, and PGSE NMR Investigation on the Relevant Role of Aggregation on the Second Order Response in CHCl3 of the Push−Pull Chromophores [5-[[4′-(Dimethylamino)phenyl]ethynyl]-15-[(4′′-nitrophenyl)ethynyl]-10,20-diphenylporphyrinate] M(II) (M = Zn, Ni)

This work has produced experimental and theoretical evidence for the independence, on the nature of the metal, of the second order NLO response of [5-[[4′-(dimethylamino)phenyl]ethynyl]-15-[(4′′-nitrophenyl)ethynyl]-10,20-diphenylporphyrinate]M(II) NLO chromophores (M = Zn, Ni). EFISH measurements, carried out at a nonresonant 1.907 μm incident wavelength and at variable concentrations in CHCl3 or in a polar and donor solvent such as DMF or by addition of an excess of pyridine to a CHCl3 solution, have shown, together with a PGSE NMR investigation, that the different second order NLO response obtained in CHCl3 for Zn(II) and Ni(II) NLO chromophores is due to a different aggregation in CHCl3 solution. Theoretical DFT/TDDFT calculations on the NLO properties of dimeric aggregates of the NLO chromophores containing the Zn(II) center have suggested, in agreement with EFISH measurements and PGSE NMR investigation, a J aggregation which induces a doubling of the second order NLO response. The PGSE NMR investigation has also suggested a much weaker dipolar interaction for the dimerization process of the NLO chromophores containing the Ni(II) center. In this latter case the antiparallel alignment of the dipole moments of the two chromophores produces a lower second order NLO response, as experimentally observed in CHCl3 solution by increasing concentration.

Electronic Characterisation and Significant Second‐Order NLO Response of 10,20‐Diphenylporphyrins and Their ZnII Complexes Substituted in the meso Position with π‐Delocalised Linkers Carrying Push or Pull Groups

AbstractThis work describes the synthesis and the electronic characterisation by electronic absorption spectroscopy, cyclic voltammetry and dipole moments of diphenyl porphyrins and their ZnII complexes substituted at the meso position by a pseudo‐linear π‐delocalised substituent carrying an electron‐donor or an electron‐withdrawing group. The second‐order NLO response was investigated by the EFISH technique working with a nonresonant incident wavelength of 1.907 μm. This work confirms the ambivalent role of the polarisable porphyrin ring, which, already in the ground state, acts as a donor or acceptor depending on the nature (acceptor or donor) of the substituent in the meso position, as was pointed out in our previous work on tetraphenyl porphyrins substituted at the β‐pyrrolic position. The second‐order NLO response has been discussed by comparing the nature of the substituent (electron donor or acceptor) and the kind of substitution (β pyrrolic or meso). This comparison evidenced a significant increase of the electron‐donor properties of NBu2 or NMe2 when they are connected to the meso position or to the β‐pyrrolic position, probably because of an auxiliary donor effect of the electron‐rich porphyrin ring. When the substituent is the electron‐withdrawing NO2 group, the substituent position (meso or β pyrrolic) is influential, with the existance of a significant increase in the second order NLO response when substitution occurs at the meso position. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The effect on E-stilbazoles second order NLO response by axial interaction with M(II) 5,10,15,20-tetraphenyl porphyrinates (M = Zn, Ru, Os); a new crystalline packing with very large holes

The axial coordination of push–pull E-stilbazoles carrying electron donor or electron withdrawing groups with tetraphenylporphyrinates of Zn(II), Ru(II) and Os(II) does not produce any significant increase in second order NLO response, the exception being the E-stilbazole carrying the electron withdrawing CF 3 group. The lack of an increase in the second order NLO response due to the polarising action on the E-stilbazole push–pull system, by the metal centres acting as Lewis acids, is attributed to the axial π backbonding of the metal atom to the E-stilbazole, such backbonding producing a screening effect that opposes σ donation. This effect becomes dominant when the E-stilbazole carries a strong electron withdrawing group. Thus, it appears that the metals in porphyrin complexes may behave in a dual way when they interact axially with soft π delocalised ligands, such as E-stilbazoles where σ acceptor or π donor properties prevail according to the nature of the E-stilbazole itself. Infrared, electronic spectra and dipole moments suggest both axial and equatorial dissipation of the electronic density located on the metal, via π backbonding processes which influence the Lewis acid behaviour of the metal centres. A particular crystal packing, with boxes formed by four porphyrinic moieties and with large empty channels within the boxes, appears to be characteristic of axially substituted tetraphenylporphyrinates, resulting in materials able to absorb gases and solvents in their void spaces.

Tautomeric enhancement of the hyperpolarizability in new acridine-benzothiazolylamine based NLO chromophores

The second order NLO response of a new family of acridine-based chromophores is greatly enhanced due to the presence of a tautomeric minor form with high charge-transfer capabilities.

A multitechnique investigation of the second order NLO response of a 10,20-diphenylporphyrinato nickel(II) complex carrying a phenylethynyl based push-pull system in the 5- and 15-positions

A multitechnique investigation of the determination of the order of magnitude of the second and third order NLO response of [5-[(4-dimethylaminophenyl)ethynyl]-15-[(4-nitrophenyl)ethynyl]-10,20-diphenylporphyrinato]nickel(II) (1) is reported with the aim to produce self consistent evidence for a significant NLO response of this kind of push-pull porphyrin chromophore. The experimental multitechnique approach is based on the EFISH technique, working with a non-resonant incident wavelength of 1.907 μm, on the solvatochromic method and finally on a vibrational method, avoiding any fluorescence or resonance interference. A theoretical MNDO-TDHF evaluation of the zero-frequency quadratic and cubic hyperpolarizabilities of an ab initio optimized planar structure is also reported. The order of magnitude of the quadratic hyperpolarizability of (1) at zero frequency (β0), was found to be significantly lower than that reported for the corresponding Cu (II) or Zn (II) complexes with the same push-pull porphyrin chromophore.

Dynamics of space charge distributions in side-chain PPV LEDs

A single wavelength electro-optical reflection technique was used to study the creation of space charge distributions (SCDs) in an Al/PPV/ITO LED by monitoring the third order NLO response of the electro-luminescent layer, at a wavelength far from the main absorption band ( λ=632.8 nm). The polymer is a PPV derivative with oxidiazole groups grafted as side chains. The measurements show the presence of SCD given by the sum of a static contribution close to the ITO, and of a slowly changing and bias dependent one due to mobile charges injection. Taking into account Debye–Hückel screening in the polymer, we estimate the density of the fixed charges to be ρ 0=1.5×10 24 m −3, for a uniform distribution in a 110 nm thick layer. The dynamics of the mobile charges was investigated by time-dependent measurements. The samples were biased at a voltage V b for a time interval and the time dependence of the signal was studied after switching off V b. The measurements were performed for several temperatures between 60 and 110°C, indicating complex dynamics of the signal. Measurements performed at low temperature (88 K) show the features of dispersive transport. The dynamic measurements were investigated by the electro-absorption technique also, with wavelengths laying in the main absorption band of PPV.