DFT study on second-order nonlinear optical properties of Pt (Ⅱ) complexes with different chromophores

DFT B3LYP/LANL2DZ method was employed to calculate electron properties and the second-order nonlinear optical(NLO) respond of platinum(Ⅱ) complexes which have been synthesized by Weinstein group.4,7-diphenyl-1,10-phenanthroline shows the ability to push electron in these complexes.Metal Pt plays a balancing charge role.Comparing complex 1b-6b with complex a,the βvec value of complex 1b-5b is larger than one of complex a,while the βvec value of complex 6b is smaller than one of com-plex a.In these seven comp...     

Theoretical study on second-order nonlinear optical properties of 1,10-phenanthroline Ru(Ⅱ) complexes

The dynamic first hyperpolarizabilities of a series of 1,10-phenanthroline Ru(Ⅱ) complexes were carried out using density functional theory(DFT).The results indicate that these complexes have large second-order nonlinear optical(NLO) responses.Specially,complex 6b has a maximal first hyperpolarizability βtot value.The first hyperpolarizabilities can be tuned by changing the ancillary ligand,introducing electron-acceptor group NO2 and/or increasing π-conjugation on phenanthroline.Calculations on absorption spectra demonstrate that the second-order NLO responses of complexes in series a are ascribed to the intraligand charge transfer(ILCT),while the complexes in series b exhibit metal-to-ligand charge transfer(MLCT) and ligand-to-ligand charge transfer(LLCT) transition at relatively low-energy absorptions.     

Theoretical investigation of nonlinear optical behavior for rod and T-Shaped phenothiazine based D-π-A organic compounds and their derivatives

The exploration of novel materials with excellent nonlinear optical (NLO) features is an area of frontline investigation for scientific community from technological point of view. This study reports the novel phenothiazine-based rod-shaped and T-shaped NLO molecules which are quantum chemically designed from synthesized compounds: rod-shaped (CFA and CBA) and T-shaped (CTA, CCA and CPA). Structural tailoring was performed on D-π-π-A centered CPA chromophore and the effect of various π-spacers, as well as solvents on NLO response properties is investigated. Density functional theory (DFT) along with time dependent DFT (TDDFT) calculations have been executed at B3LYP/6-311G(d,p) functional to examine entire analysis. Results showed a smaller energy gap in structurally modified compounds as compared to reference CPA. Global reactivity parameters analysis revealed smaller hardness and larger softness values in T-shaped compounds. UV–Vis analysis of investigated molecules displayed a red shift in absorption maximum value as compared to CPA. Natural bond orbital (NBO) and frontier molecular orbital (FMO) analysis revealed the stability and intra-molecular electron transferring (ICT) process in investigated molecules. ICT showed the effective charge shift from donor to acceptor via π-spacers. Overall, promising NLO response exists in gas phase and different solvents (acetonitrile, ethyl alcohol and water). Interestingly, proposed molecule CPP presented a maximum value of linear polarizability < α > as 1518.23 a.u and first hyperpolarizability (β_tot) as 755322.39 a.u in acetonitrile solvent. In short, entitled chromophores exhibited excellent NLO properties due to their lower charge transport resistance. This NLO study may open a new topic for researchers to discover novel NLO for hi-tech submissions of modern era.     

Ferrocenyl D-π-A conjugated polyenes with 3-dicyanomethylidene-1-indanone and 1,3-bis(dicyanomethylidene)indane acceptor groups: Synthesis, linear and second-order nonlinear optical properties and electrochemistry

Second-order nonlinear optical chromophores incorporating the ferrocenyl group as an electron donor and 3-dicyanomethylidene-1-indanone and 1,3-bis(dicyanomethylidene)indane acceptor groups, connected by a conjugated polyenic bridge of varied length (2[n] and 3[n], respectively) have been synthesized. The electronic absorption spectra of these compounds display in the visible region bands attributable to π-π* and metal-to ligand charge transfer (MLCT) transitions. The energies of these transitions are close to those reported earlier for ferrocenyl D-π-A chromophores with the strongest acceptor groups, e.g., with the 3-dicyanomethylidene-2,3-dihydrobenzothiophene-1,1-dioxide group (1[n]) [V. Alain, M. Blanchard-Desce, C.-T. Chen, S.R. Marder, A. Fort, M. Barzoukas, Synt. Met. 81 (1996) 133]. The solid-state structure of 2[3], determined by X-ray diffraction shows a significant reduction of the bond length alternation (BLA), 0.05 Å, suggesting high first hyperpolarizability. However, a centrosymmetrical packing of molecules of this compound in the crystal excludes its second harmonic generation ability. The μβ values of 2[n] and 3[n], determined by the EFISH technique at 1907 nm are high and increase with the increasing length of the conjugated π-bridge. The highest value of μβ (8720 × 10⁻⁴⁸ esu) was determined for 3[4], which is close to that reported for 1[4] (11 200 × 10⁻⁴⁸ esu), the highest value found for a ferrocenyl D-π-A chromophore until now.     

Quantum chemical study of redox-switchable second-order optical nonlinearity in Keggin-type organoimido derivative [PW11O39(ReNC6H5)] n− (n = 2–4)

To analyze the effect of redox state changes on the second-order nonlinear optical (NLO) responses of organoimido-functionalized Keggin-type heteropolyanions, the excitation properties and static second-order polarizabilities of fully oxidized state, the first and second reduced states were calculated by means of the time-dependent density functional theory (TDDFT) method combined with the sum-over-states (SOS) formalism. The incorporation of extra electrons causes significant enhancement in the second-order NLO activity. The reduced complexes show more than three times the efficiency of fully oxidized state. Moreover, the NLO activities for PW₁₁Re^VNPh system can also be modified by controlling the spin multiplicity. The high spin state (³ 3) has twice larger β _vec value than the low spin state (¹ 3). The characteristic of the charge-transfer transition corresponding to the dominant contributions to the β _vec values indicates that metal-centered redox processes influence the intramolecular donor or acceptor character, which accordingly leads to the variations in the computed β values. Owing to the reversible and manipulable redox processes, these kinds of the POM-based hybrid complexes could comprise a promising family of three-state redox-switchable molecular device combining chromic, magnetic, and NLO output.     

A theoretical study of an unusual Y-shaped three-coordinate Pt complex: Pt(0) σ-disilane complex or Pt(II) disilyl complex?

The unusual Y-shaped structure of the recently reported three-coordinate Pt complex Pt[NHC(Dip)(2)](SiMe(2)Ph)(2) (NHC = N-heterocyclic carbene; Dip = 2,6-diisopropylphenyl) was considered a snapshot of the reductive elimination of disilane. A density functional theory study indicates that this structure arises from the strong trans influence of the extremely σ-donating carbene and silyl ligands. Though this complex can be understood to be a Pt(II) disilyl complex bearing a distorted geometry due to the Jahn-Teller effect, its (195)Pt NMR chemical shift is considerably different from those of Pt(II) complexes but close to those of typical Pt(0) complexes. Its Si···Si bonding interaction is ~50% of the usual energy of a Si-Si single bond. The interaction between the Pt center and the (SiMe(2)Ph)(2) moiety can be understood in terms of donation and back-donation interactions of the Si-Si σ-bonding and σ*-antibonding molecular orbitals with the Pt center. Thus, we conclude that this is likely a Pt(0) σ-disilane complex and thus a snapshot after a considerable amount of the charge transfer from disilane to the Pt center has occurred. Phenyl anion (Ph(-)) and [R-Ar](-) [R-Ar = 2,6-(2,6-iPr(2)C(6)H(3))(2)C(6)H(3)] as well as the divalent carbon(0) ligand C(NHC)(2) also provide similar unusual Y-shaped structures. Three-coordinate digermyl, diboryl, and silyl-boryl complexes of Pt and a disilyl complex of Pd are theoretically predicted to have similar unusual Y-shaped structures when a strongly donating ligand coordinates to the metal center. In a trigonal-bipyramidal Ir disilyl complex [Ir{NHC(Dip)(2)}(PH(3))(2)(SiMe(3))(2)](+), the equatorial plane has a similar unusual Y-shaped structure. These results suggest that various snapshots can be shown for the reductive eliminations of the Ge-Ge, B-B, and B-Si σ-bonds.     

Quantum chemical study of pyridine addition to Ni(II) β-diketonate complexes

The addition reaction of two pyridine molecules to Ni(II) β-diketonate bis-chelate was studied by quantum chemical density functional theory calculations (B3LYP/6-311++G(d, p)). The addition of the first pyridine molecule to the trans-position was found to be the most favorable channel for this two-stage process; the reaction is accompanied by a change in the spin state of the system. The transition between the potential energy surfaces of different multiplicity occurs at the first stage without considerable energy expenditure; the addition of the second pyridine molecule is barrierless.     

Structural and photophysical studies of triphenylamine-based nonlinear optical dyes: effects of π-linker moieties on the D-π-A structure

In this work, a series of eight metal-free organic dyes based on triphenylamine as a donor and cyanoacetic acid as an acceptor of electrons with the donor-π-acceptor structure were studied by DFT and TD-DFT methods. Their electronic properties, absorption spectra, and molecular nonlinear optical (NLO) responses have been analyzed and reported. The influence of the change of π-conjugated linker on the electrochemical and photophysical properties of these metal-free organic dyes has been investigated and discussed in detail. The energy gap decreases by going from L1 to L8, which causes a large NLO response for the studied dyes. The natural bond orbital (NBO) analysis reveals that the separation of charge occurred upon photoexcitation and the electrons moved from the donor to the acceptor moiety. A high NLO response reveals that this kind of metal-free organic dyes has eye-catching and remarkably large first hyperpolarizability β_tot values, especially for L7 ((E)-2-cyano-3-(3-((E)-2-(3-((E)-4-(diphenylamino)styryl)benzo[c]thiophen-1-yl)vinyl)benzo [c]thiophen-1-yl)acrylic acid) and L8 ((E)-2-cyano-3-(7-((E)-2-(7-((E)-4-(diphenylamino)styryl)thieno[3,4-b]pyrazin-5-yl)vinyl)thieno[3,4-b]pyrazin-5-yl)acrylic acid) with 150423.50 (a.u) and 202773.63 (a.u), respectively. Our research has been carried out to extend the conjugation of organic materials by controlling their π-conjugated linker to design new appealing NLO compounds. This study shows that these dyes are promising and have special properties for modern hi-tech applications such as solar cells, transistors, and organic light-emitting diodes (OLEDs), and even these properties can be adjusted and enhanced by the incorporation of the benzothiophene or thienopyrazine derivatives as a bridge so as to improve from L7 to L8.     

Donor-(π-bridge)-azinium as D-π-A+ one-dimensional and D-π-A(+)-π-D multidimensional V-shaped chromophores

Heteroaromatic cations reacted with N-heteroarylacetylenes under Sonogashira conditions to allow easy access to potential single donor D-π-A(+) and V-shaped D-π-A(+)-π-D chromophores, where the acceptor moiety A is the π-deficient pyridinium cation and the donor moiety is represented by different π-excessive N-heterocycles. The β hyperpolarizabilities were measured using hyper-Rayleigh scattering experiments and the experimental data are supported by a theoretical analysis that combines a variety of computational procedures, including Density Functional Theory (DFT) and correlated Hartree-Fock-based methods (RCIS(D)).     

DFT study of chemical mechanism of pre-SERS spectra in Pyrazine–metal complex and metal–Pyrazine–metal junction

The chemical mechanism of Normal Raman Scattering (NRS) and pre-surface enhanced Raman scattering (pre-SERS) spectra for Pyrazine–Ag₂ complex, Ag₂–Pyrazine–Ag₂ junction and Ag₂–Pyrazine–Au₂ junction were investigated with density functional theory (DFT) and charge difference densities (CDDs) for the first time. The NRS intensities of the above three structures enhanced obviously relative to isolated Pyrazine and the enhancement mechanism was confirmed to be static chemical enhancement. The pre-SERS intensities of the above three structures enhanced evidently compared to corresponding NRS intensities, and the enhancement mechanism was confirmed to charge transfer (CT) resonance Raman enhancement. The largest enhanced orders of NRS and pre-SERS intensities among the three structures were up to 10³ and 10⁵, respectively. Compared the intensity of pre-SERS with corresponding intensity of NRS spectra, the enhancement effect of Pyrazine–Ag₂ complex was larger than the others. Intramolecular and intermolecular CT on resonant electronic transition were described by CDDs.     

A vibrational study of the metal—olefin bond in norbornadiene complexes of Rh(I), Pd(II) and Pt(II)

Vibrational assignments of the complexes [RhClC₇H₈]₂, PtCl₂C₇H₈, and PdCl₂C₇H₈ have been undertaken. A reinvestigation of the norbornadiene spectrum was necessary and a new set of assignments is given. The shift in energy of bands I and II and the out-of-plane olefinic CH wagging modes, as well as the relative energies of the bands associated with the metal—olefin motions are consistent with the total metal—norbornadiene interaction following the order Rh>Pt>Pd and the extent of the π component being ordered as Rh⋍Pt>Pd.     

Computational study on second-order nonlinear optical (NLO) properties of a novel class of two-dimensional Λ- and W-shaped sandwich metallocarborane-containing chromophores

We systematically investigate the linear optical properties and the static second-order nonlinear optical (NLO) properties on a series of two-dimensional (2D) D-π-A-π-D/A-π-D-π-A sandwich metallocarborane-containing molecules with density functional theory (DFT). It can be found that the substitution effect has an influence on the electronic absorption and NLO responses of the 2D molecules. For example, the ${\beta }_{vec}$ value is sensitive to the substitution from amino (–NH₂) to nitryl (–NO₂); the angle between the two A–D branches significantly affects the dipole moment and ${\beta }_{vec}$ value. In addition, time-dependent DFT calculations and the analysis of major molecular orbitals predict that the sandwich metallocarborane acts as an electron donor better than electron acceptor. Furthermore, the two strong synchronized charge transfer (CT) coming from the two branches and p–π (B_2p–C≡C) conjugation contributes to the second-order polarizabilities in our studied systems.     

Near-infrared-emitting phthalocyanines. A combined experimental and density functional theory study of the structural, optical, and photophysical properties of Pd(II) and Pt(II) α-butoxyphthalocyanines

The structural, optical, and photophysical properties of 1,4,8,11,15,18,22,25-octabutoxyphthalocyaninato-palladium(II), PdPc(OBu)(8), and the newly synthesized platinum analogue PtPc(OBu)(8) are investigated combining X-ray crystallography, static and transient absorption spectroscopy, and relativistic zeroth-order regular approximation (ZORA) Density Functional Theory (DFT)/Time Dependent DFT (TDDFT) calculations where spin-orbit coupling (SOC) effects are explicitly considered. The results are compared to those previously reported for NiPc(OBu)(8) (J. Phys. Chem. A 2005, 109, 2078) in an effort to highlight the effect of the central metal on the structural and photophysical properties of the group 10 transition metal octabutoxyphthalocyanines. Different from the nickel analogue, PdPc(OBu)(8) and PtPc(OBu)(8) show a modest and irregular saddling distortion of the macrocycle, but share with the first member of the group similar UV-vis spectra, with the deep red and intense Q-band absorption experiencing a blue shift down the group, as observed in virtually all tetrapyrrolic complexes of this triad. The blue shift of the Q-band along the MPc(OBu)(8) (M = Ni, Pd, Pt) series is interpreted on the basis of the metal-induced electronic structure changes. Besides the intense deep red absorption, the title complexes exhibit a distinct near-infrared (NIR) absorption due to a transition to the double-group 1E (π,π*) state, which is dominated by the lowest single-group (3)E (π,π*) state. Unlike NiPc(OBu)(8), which is nonluminescent, PdPc(OBu)(8) and PtPc(OBu)(8) show both deep red fluorescence emission and NIR phosphorescence emission. Transient absorption experiments and relativistic spin-orbit TDDFT calculations consistently indicate that fluorescence and phosphorescence emissions occur from the S(1)(π,π*) and T(1)(π,π*) states, respectively, the latter being directly populated from the former, and the triplet state decays directly to the S(0) surface (the triplet lifetime in deaerated benzene solution was 3.04 μs for Pd and 0.55 μs for Pt). Owing to their triplet properties, PdPc(OBu)(8) and PtPc(OBu)(8) have potential for use in photodynamic therapy (PDT) and are potential candidates for NIR light emitting diodes or NIR emitting probes.     

Synthesis and properties of ms- and β-substituted Pt(II) and Pt(IV) tetraphenylporphyrinates

The interaction of 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra-(4-chlorophenyl)porphyrin, 2-bromo-5,10,15,20-tetraphenylporphyrin, and 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin with platinum(II) chloride in boiling phenol has been studied. The corresponding platinum(II) porphyrinates have been synthesized; their subsequent treatment with bromine in chloroform resulted in platinum(IV) porphyrinates. The Pt(II) and Pt(IV)(Br)₂ porphyrinates have been identified by elemental analysis, electron absorption, IR, and ¹H NMR spectroscopy.     

Solvent extraction of metal ions with mixed ligands—I: Adduct formation of Cu(II) and Zn(II) chelate complexes of thenoyltrifluoroacetone and β-isopropyltropolone

The following equilibria have been studied by distribution measurements with radioisotopes:The formation of MA₂ M²⁺(aq) + 2HA(org) ⇌ MA₂(org) + 2H⁺(aq)The adduct formation between MA₂ and L MA₂(org) + nL(org) ⇌ MA₂L_n(org) where M  Cu or Zn HA = thenoyltrifluoroacetone (TTA) or β-isopropyltropolone (IPT) L = tributyl phosphate (TBP), methyl isobutyl ketone (hexone) or undissociated IPT (HA) org = hexone, chloroform or carbon tetrachloride aq = 0·1 M (H, Na)ClO₄The experimental results are shown in Figs. 1–12. Stability constants have been determined for the different systems and are summarized in Table 1. The experiments show the presence of both MA₂ complexes and MA₂L complexes. Some indications of ZnA₂L₂ are found. The relative strengths of complexes (values of the stability constants) show that the TTA complexes form more stable adducts than the IPT complexes, and that CuA₂ has a smaller tendency to form an adduct than ZnA₂. TBP forms more stable adducts than hexone.     

Effects of external electric field and self-aggregations on conformational transition and optical properties of azobenzene-based D-π-A type chromophore in THF solution

The influence of environments (THF solvents and electric field) and molecular self-aggregations on the structure and optical properties of 4-(4-hydroxyphenylazo)nitrobenzene has been investigated by molecular dynamics (MD) simulations and quantum chemical calculations. Long-range electrostatic effects and the hydrogen bond interactions between the solute and the THF solvent molecules lead to the augments of nonlinear optical (NLO) response by about two times from the gas phase to THF solution, accompanied by considerable red-shift of more than 40 nm in the maximum absorption wavelengths of the ground (S(0)) and low-lying excited states (S(1), S(2), and S(3)). The solvated chromophore reorients quickly (within 300 ps) under external electric field of 1.0 V/nm, even when the direction of the applied electric field is antiparallel to the dipole moment of the solute. Nonequilibrium MD simulations demonstrate that the light-induced cis-trans isomerization in THF solution and external electric field need longer relaxation time (about 1.0 ps) than that in gas phase (about 500 fs). The dipole-dipole interactions and intermolecular hydrogen bonds facilitate the self-aggregations of solute molecules in solution. The V-shaped dimer exhibits higher hyperpolarizability value by about 1.2 times of the monomer, whereas the antiparallel alignment leads to a cancellation of dipole moment and hence dramatic decrease in hyperpolarizability (one-third of the monomer). However, the Boltzmann-weighted contribution to hyperpolarizability from these two aggregations (with 82% V-shaped and 18% antiparallel) is close to that of the monomer. Orientations of D-π-A dipoles in various environments and molecular aggregations are important to modulate the optical properties of materials.     

Novel metal complexes of pyridineimine derivative used as auxiliary electron acceptor of D-(A-π-A)2 motif dye sensitizer: synthesis and photovoltaic application

Journal of Solid State Electrochemistry - The auxiliary acceptors of metal complexes can easily regulate the electron-withdrawing ability of electron acceptor and adjust the balance of...     

Microcalorimetric study of DNA–Cu(II)TOEPyP(4) porphyrin complex

The influence of new water soluble cationic metalloporphyrin Cu(II)TOEPyP(4) (meso-tetra-(4-N-oxyethylpyridyl)), analogue of Cu(II)TMPyP(4), on thermodynamic stability of DNA at various molar ratios of r = porphyrin/DNA b.p. (0 < r < 0.12) has been studied. It has been shown that Cu(II)TOEPyP(4) is a strong stabilizing agent for calf thymus DNA increasing its melting temperature from 75.5 to 99.5 °C, in the range 0 < r < 0.06. The melting enthalpy (∆H _m) does not change in the range 0.002 < r < 0.06 and it equals to 11.6 ± 0.8 cal/g. At r > 0.07, ∆H _m and T _m decrease, and at r = 0.12 they equal to 6.4 ± 0.6 cal/g and 92.5 °C, accordingly. We suggest that such centers of binding are the well documented 5′CG3′ sites and G-quadruplex at r < 0.01, and negatively charged phosphate groups at r > 0.01. On the basis of ∆H _m invariability with simultaneous increase of T _m in the range 0.002 < r < 0.06, it is shown that the DNA-Cu(II)TOEPyP(4) complex melting is not of an enthalpic nature but of an entropic one. The two-phase helix–coil transition of DNA at r < 0.01 is considered as a result of porphyrin redistribution in the melting process.