Functionalized styryl iridium(III) complexes as active second-order NLO chromophores and building blocks for SHG polymeric films

International audienceWe studied the second-order NLO properties in solution of various Ir(III) acetylacetonate complexes bearing a substituted cyclometallated 4-styryl-2-phenylpyridine (ppy-4-styryl-R, with R = NEt2, OMe, H, NO2) with the EFISH technique. The dipole moments were evaluated by Density Functional Theory (DFT) calculations. We have also investigated the Second Harmonic Generation (SHG) of composite films based on the various cyclometallated Ir(III) complexes dispersed and oriented in a polymethylmethacrylate (PMMA) matrix

Роль семьи в процессе первичной социализации в отечественной и зарубежной литературе

A series of 5,15 push–pull <i>meso</i>-diarylzinc­(II) porphyrinates, carrying one or two −COOH or −COOCH₃ acceptor groups and a −OCH₃ or a −N­(CH₃)₂ donor group, show in <i>N</i>,<i>N</i>-dimethylformamide and CHCl₃ solutions a negative and solvent-dependent second-order nonlinear-optical (NLO) response measured by the electric-field-induced second-harmonic generation (EFISH) technique, different from the structurally related zinc­(II) porphyrinate carrying a −N­(CH₃)₂ donor group and a −NO₂ acceptor group, where a still solvent-dependent but positive EFISH second-order response was previously reported. Moreover, when a −N­(CH₃)₂ donor group and a −COOH acceptor group are part of a sterically hindered 2,12 push–pull β-pyrrolic-substituted tetraarylzinc­(II) porphyrinate, the EFISH response is positive and solvent-independent. In order to rationalize these rather intriguing series of observations, EFISH measurements have been integrated by electronic absorption and IR spectroscopic investigations and by density functional theory (DFT) and coupled-perturbed DFT theoretical and ¹H pulsed-gradient spin-echo NMR investigations, which prompt that the significant concentration effects and the strong influence of the solvent nature on the NLO response are originated by a complex whole of different aggregation processes induced by the −COOH group

Nonlinear optical properties of intriguing Ru σ-acetylide complexes and the use of a photocrosslinked polymer as a springboard to obtain SHG active thin films

This work reports on the design, synthesis and photo-physical properties of two ruthenium σ-alkynyl complexes. It is shown that, despite similar optical absorption features recorded in solution, the introduction of a benzaldehyde moiety leads to an improved non-linear optical (NLO) response as measured by Electric Field Induced Second Harmonic (EFISH) generation and Third Harmonic Generation (THG) at 1.907 μm, both related to the second order hyperpolarizability. These structure–property relationships are rationalized based on few state modelling. Complex 2 is subsequently processed to afford composite films that demonstrate a χ2 of 1.4 pm V−1, quite remarkable given the ease of film processing implemented in this work

An investigation on the second-order nonlinear optical response of cationic bipyridine or phenanthroline iridium(iii) complexes bearing cyclometallated 2-phenylpyridines with a triphenylamine substituent

This work was supported by MIUR, CNR and the National Interuniversity Consortium of Materials Science and Technology (Project INSTMMI012) in Italy. C.H. acknowledges Région Bretagne, France, for funding. E.Z.-C. acknowledges the University of St Andrews and EPSRC (EP/M02105X/1) for financial support.The synthesis and characterisation of six new cationic iridium(iii) complexes bearing either 4,4′-di-tert-butyl-2,2′-bipyridine (dtBubpy) or 5-NO2-1,10-phenanthroline along with two cyclometallated 2-phenylpyridine derivative ligands, decorated with triphenylamine groups either meta or para to the Ir-CC^N bond or para to the Ir-NC^N bond, are reported. The second-order nonlinear optical (NLO) properties of all the compounds have been determined by the electric field induced second harmonic generation technique and show that the μβEFISH value can be tuned by the nature of the iridium coordination sphere. The dipole moment, μ, necessary to evaluate the quadratic hyperpolarizability βEFISH, was theoretically determined. The linear optical properties of the complexes are also presented and rationalised by quantum-chemical calculations. One of the prepared iridium compounds was incorporated into a polystyrene film, affording the first example of a second-order NLO active polymeric film based on a cationic organometallic complex.PostprintPeer reviewe

Push-pull unsymmetrical substitution in nickel(II) complexes with tetradentate N2O2 Schiff base ligands: Synthesis, structures and linear-nonlinear optical studies

New push-pull (A-D) nickel(II) compounds of general formula [Ni(5-A-5'-D-saltn)] (3a-3l) with unsymmetrically-substituted N2O2 tetradentate Schiff base ligands are reported here. The ligands 5-A-5'-D-saltn(2-) (H(2)saltn = N,N'-bis(salicylidene) diaminopropane) possess differently-substituted salicylaldehyde ((A/D)sal) moieties condensed to 1,3-diaminopropane (tn), and carry either an electron acceptor (A = H, Br, or NO2) or donor (D = H, Me, or OMe) group in the para position with respect to the coordinated phenoxido oxygen atoms. These compounds could be obtained by template synthesis involving derivatives [Ni(Gsal)(2)(H2O)(2)], 1a-e (G = NO2, Br, H, Me and OMe, respectively) and [Ni(L-G)2], 2a-d (L-G-= (E)2-(( 3-aminopropylimino) methyl)-4-G-phenolate, G = NO2, Br, H and Me, respectively). Scrambling of the ligands and condensation to compounds 3 was suitably achieved by refluxing compounds 1 and 2 that carry the G groups suitable for the desired final A-D combination. Dinuclear intermediates [Ni-2(mu-L-G)2((')G'sal)(2)] (4a, b, e, f, g) were also detected and isolated. The single-crystal X-ray diffraction structures of [Ni(5'-OMe-saltn)]center dot CHCl3 (3c center dot CHCl3), [Ni(5-Br-5'-OMe-saltn)]center dot EtOH (3g center dot EtOH) and [Ni(5-NO2-saltn)] (3j) show different degrees of distortion around the central core, leading to saddle-like (3c), planar (3g) and step-like (3j) molecular conformations. DFT geometrical optimization of the compounds showed that, for isolated molecules, the saddle-like conformation is slightly more stable with respect to the other conformations. UV-visible absorption spectra showed structured absorption profiles at about 320-440 nm, whose intensity was amplified by the presence of the nitro group, and this was assigned to a convolution of one metal-to-ligand charge transfer and two intra-ligand charge transfer transitions by TDDFT computations. Surprisingly, UV-visible spectra of the derivatives with Br were comparable to the derivatives with Me, suggesting that in this case the behaviour of the halogen was as a weak electron donor group. The experimental investigation (through electric-field-induced second-harmonic and solvatochromic measurements) of the second-order NLO responses of compounds 3, in conjunction with the theoretical calculations, revealed that the observed NLO efficiency is determined by the combined effect of two almost orthogonal charge transfer directions within the molecules, one along the axis approximately bisecting the donor and the accepting moieties and the other along the A-D axis

Copper(II) Complexes of salen Analogues with Two Differently Substituted (Push-Pull) Salicylaldehyde Moieties. A Study on the Modulation of Electronic Asymmetry and Nonlinear Optical Properties

This paper presents some copper(II) complexes of salen analogues in which the two salicylaldehyde moieties carry different (electron donor, D, and acceptor, A) substituents in position 5, producing a push-pull charge asymmetry. The X-ray structures of some compounds show the presence of pairs of stacked molecules with head-to-tail intermolecular associations. The geometries of all complexes have been optimized through density functional theory (DFT) studies, which have shown that a major influence on the coordination bond lengths is given by the presence of the electron acceptor NO2 group. Such an influence operates mainly on the Cu-phenolato bonds: elongation of the Cu-O distance of the 5-nitrosalicylaldehyde moiety, with a concomitant decrease of the other Cu-O distance; the Cu-N bonds are less affected. The D groups have only a minor influence. The nonlinear optical responses, mu(g)beta(vec), of some molecules have been determined by EFISH measurements, and the beta(vec) values have been obtained using the DFT-calculated mu(g) values because solubility problems hampered the experimental measurements of mu(g) of some derivatives; the former, however, have been found to be in agreement with the experimental values that could be obtained. Deconvolution of the absorption bands in the near-UV region has allowed recognition of the charge-transfer (CT) transition, assigned to a ligand-to-metal CT (LMCT) by time-dependent DFT computations; we have then used the solvatochromism of this transition to obtain beta(0) and beta(CT) values using the two-state model. These values were compared with those obtained by computational studies, which have also allowed evaluation of the influence of the substituents on the directions of mu(g) and beta(tot)

synthesis chiroptical and shg properties of polarizable push pull dyes built on π extended binaphthyls

Novel binaphthyl push–pull dyes extend their π-bridge and incorporate as acceptors pyridine units, useful for further supramolecular polarization

A Chiral Bis(salicylaldiminato)zinc(II) Complex with Second-Order Nonlinear Optical and Luminescent Properties in Solution

Whereas there is an increasing amount of reports on the second-order nonlinear optical (NLO) and luminescence properties of tetradentate [N2O2] Schiff base&ndash;zinc complexes, the study of zinc complexes having two bidentate [NO] Schiff-base ligands is relatively unexplored from an NLO point of view. This work puts in evidence that the known chiral bis{2-[(R)-(+)-1-phenylethyliminomethyl]phenolato-N,O}zinc(II) complex is a fascinating multifunctional molecular inorganic&ndash;organic hybrid material characterized by interesting second-order NLO and luminescent properties in solution. The emissive properties of the organic 2-(R)-(+)-1-phenylethyliminomethyl]phenol proligand are greatly enhanced upon coordination to the inorganic Zn(II) center

An investigation on the second-order NLO properties of novel cationic cyclometallated Ir(III) complexes of the type [Ir(2-phenylpyridine)2(9-R-4,5-diazafluorene)]+ (R = H, fulleridene) and the related neutral complex with the new 9-fulleriden-4-monoazafluorene ligand

Novel cationic cyclometallated Ir(III) complexes bearing diaza- or monoazafluorene substituted or not with a C60-fullerene moiety have been synthesized together with a novel interesting ligand 9-fulleriden-4-monoazafluorene and the related Ir(III) neutral complex [Ir(ppy)2(9-fulleriden-4-monoazafluorene)]. All complexes show a negative large value of μβ1.907 (−600 to −2190 × 10−48 esu), as determined by the Electric Field Induced Second Harmonic generation (EFISH) technique working at 1.907 μm in 10−3 M CH2Cl2 solution. The NLO response increases upon introduction of the fullerene moiety, due to a decrease of the interaction forces between the anion and cation within the ion pair which leads to an increase of the percentage of free ions, as evidenced by diffusion NMR experiments. Besides, it appeared that for the neutral complex [Ir(ppy)2(9-fulleriden-4-monoazafluorene)] the EFISH μβ1.907 value is lower than that of cationic Ir(III) complexes, but comparable or slightly lower to the values of other neutral Ir(III) complexes such as [Ir(ppy)2(RCOCR′COR)] (ppy = cyclometallated 2-phenylpyridine; R = Me, Ph; R′ = H, 2,4-dinitrophenyl), confirming that the second-order NLO response of these neutral chromophores is dominated by ILCT processes concerning cyclometallated 2-phenylpyridines