Series Of Chromophores Research Articles

Quantum Chemical Exploration of A-π1-D1-π2-D2-Type Compounds for the Exploration of Chemical Reactivity, Optoelectronic, and Third-order Nonlinear Optical Properties.

Organic compounds exhibit significant nonlinear optical (NLO) properties and can be utilized in various areas like optical parameters, fiber optics, and optical communication. Herein, a series of chromophores (DBTD1-DBTD6) with an A-π1-D1-π2-D2 framework was derived from a prepared compound (DBTR) by varying the structure of π-spacer and terminal acceptor. The DBTR and its investigated compounds were optimized at the M06/6-311G(d,p) level of theory. Frontier molecular orbitals (FMOs), nonlinear optical (NLO) properties, global reactivity parameters (GRPs), natural bonding orbital (NBO), transition density matrix (TDM), molecular electrostatic potential (MEP), and natural population analysis (NPA) were accomplished at the abovementioned level to describe the NLO findings. DBTD6 has the lowermost band gap (2.131 eV) among all of the derived compounds. The decreasing order of highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap values was DBTR > DBTD1 > DBTD2 > DBTD3 > DBTD4 > DBTD5 > DBTD6. The NBO analysis was carried out to describe noncovalent interactions such as conjugative interactions and electron delocalization. From all of the examined substances, DBTD5 showed the highest λmax value at 593.425 nm (in the gaseous phase) and 630.578 nm (in chloroform solvent). Moreover, the βtot and ⟨γ⟩ amplitudes of DBTD5 were noticed to be relatively greater at 1.140 × 10-27 and 1.331 × 10-32 esu, respectively. So, these outcomes disclosed that DBTD5 depicted the highest linear and nonlinear properties in comparison to the other designed compounds, which underlines that it could make a significant contribution to hi-tech NLO devices.

Synthesis, optical and electrochemical properties of a series of push-pull dyes based on the 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (TCF) acceptor

A series of chromophores was designed and synthesized using 2-(3-cyano-4,5,5-trimethylfuran-2 (5H) -ylidene) malononitrile (TCF) as the electron acceptor and differing from each other by the use of thirteen different electron donors. The different dyes were characterized for their optical and electrochemical properties and theoretical calculations were also carried out to support the experimental results. By changing the electron donor in the thirteen dyes, chromophores absorbing between 430 nm and 700 nm could be synthesized. Solvatochromism of the different dyes was analyzed in 23 solvents of different polarity and a positive solvatochromism was determined for all chromophores using the semi-empirical solvent polarity scales based on the Kamlet-Taft parameters (π *) or the Catalan parameters (SdP and SPP).

To what extent are the photophysical properties of quinoxaline- and quinoxalinone-based chromophores predictable?

A series of chromophores containing quinoxaline or quinoxalinone electron-acceptor (A) and dialkylaminostyryl electron-donor (D) units linked by π electronic bridge has been synthesized. Electronic emission and absorption spectra of the novel D-π-A, D-π-A-π-D or D-π-A-π-A-π-D systems cover a broad range from ultraviolet to near infrared. Positions and relative intensities of their absorption bands are shown to depend strongly on structural modifications of the molecules, while emission in solution strongly depends on both the structure of the solute and the solvent polarity. Quantum chemical modeling provided a reliable description of the observed absorption spectra and reproduced the positions of the emission bands. Quantum yields of emission are shown to be qualitatively predictable on the basis of empirical rules connecting the luminescence intensity with the chemical structures of both quinoxaline- and quinoxalinone-based luminopohores and the polarity of the solvents used. Theoretical assessment of the character of the main electronic transitions suggests that simultaneous presence of D and A units conjugated via π-bridges ensures the intramolecular charge-transfer effects probably underlying the observed similar solvatochromism for all the studied systems irrespective of their polarity.

Development of a Highly Selective, Sensitive, and Fast Response Upconversion Luminescent Platform for Hydrogen Sulfide Detection

Hydrogen sulfide (H2S) has been recognized as one of most important gaseous signaling molecules mediated by a variety of physiological and pathological processes. Yet, its functions remain largely elusive due to the lack of potent monitoring methods. Hereby this issue is addressed with a powerful new platform—dye‐assembled upconversion nanoparticles (UCNPs). A series of chromophores with different absorption bands and fast responses towards H2S is combined with UCNPs and results in a library of H2S sensors with responsive emission signals ranging from the visible to the near‐infrared (NIR) region. These nanoprobes demonstrate highly selective and rapid responses to H2S in vitro and in cells. Furthermore, H2S levels in blood can be detected using the developed nanoprobes. Hence the reported H2S sensing platform can serve as a powerful diagnostic tool to research H2S functions and to investigate H2S‐related diseases.

NLO chromophores containing dihydrobenzothiazolylidene and dihydroquinolinylidene donors with an azo linker: Synthesis and optical properties

We report the synthesis of a series of nonlinear optical chromophores containing either a dihydrobenzothiazolylidene or dihydroquinolinylidene donor with an azo linker. The results demonstrate the versatility of coupling a diazonium salt to a donor–methylidene nucleus in order to access novel materials with good thermal stabilities and high nonlinear optical responses. From hyper-Raleigh scattering studies it was found that the use of the well-known TCF acceptor yields the best performing chromophores, one of which has a dynamic first hyperpolarizability of 1900 × 10 −30 esu at 800 nm. The results from this study suggest the use of pro-aromatic donors such as dihydrobenzothiazolylidene or dihydroquinolinylidene results in compounds with higher nonlinear optical responses than those containing donors based on either indoline or aniline . ► A series of chromophores with aromatizable donors and azo linkers are reported. ► The methodology allows for the synthesis of the target molecules in high yield. ► The compounds have first hyperpolarizabilities of up to 1900 × 10 −30 esu. ► The compounds have decomposition temperatures between approx 215–250 °C.

Molecular engineering of chromophores for combined second-harmonic and two-photon fluorescence in cellular imaging

A series of chromophores with enhanced second- and third-order nonlinear optical properties were engineered for use in combined second-harmonic and two-photon fluorescence microscopy. Electron-accepting moieties imparted nonlinear optical properties to the chromophores. The electron-rich carbazole core served as a template towards one- or two-dimensional chromophores. More efficient acceptor groups (pyridinium, benzazolium, benzothiazolium) on the carbazole donor core resulted in improved second- and third-order nonlinear optical properties. A selection of these chromophores was tested in a cellular environment with a multimodal multiphoton microscope. The structural differences of the chromophores resulted in high selectivity for mitochondria or the nucleus in two-photon fluorescence and ranging from no signal to high selectivity for mitochondria in the SHG channel.

Computational Study of Molecules with High Intrinsic Hyperpolarizabilities

In the current manuscript we present the results of a computational study on a series of chromophores with enhanced intrinsic hyperpolarizability. The high hyperpolarizability values of these molecules were previously reported and were achieved by making use of aromatic moieties in order to modulate the aromatic stabilization energy along the conjugated bridge between the donor and the acceptor. Calculations were performed using semiempirical, DFT, and TDDFT methods, and the results reproduce the trend determined experimentally for the first hyperpolarizability values. Several calculation schemes were used, and the best agreement was achieved when long-range Hartree-Fock exchange corrections and solvent effects are included in the DFT calculations. The long-range corrections proved to be especially important for the azobenzene derivatives, which otherwise have their hyperpolarizability overestimated considerably in the DFT calculations. The results are also analyzed within the framework of a two-level model, which correctly reproduces the trend in the hyperpolarizabilities of the molecules under study.

The effectiveness of essential-state models in the description of optical properties of branched push–pull chromophores

In this paper we present the synthesis, spectroscopic characterization and theoretical modelling of two pairs of correlated dipolar and octupolar donor-acceptor conjugated chromophores, based on the triphenylamine branching centre. The two pairs of chromophores differ for the electron withdrawing end-groups. Linear absorption, fluorescence and two-photon absorption of all the compounds in different solvents can be well described by the use of charge-resonance theoretical models based on essential-state descriptions of the electronic structure, and taking into account the coupling to effective molecular vibrations and to polar solvation degrees of freedom. On the contrary, the alternative Frenkel exciton model does not provide a good description of the observed behavior. The robustness of the proposed theoretical models is demonstrated for the first time by the fact that the modulation of a single molecular parameter (the one linked to the electron-withdrawing ability of the end groups) is enough to describe the evolution of the spectroscopic properties along the whole series of chromophores, both "intra-pair" and "inter-pair". The effectiveness of the approach suggests that this kind of theoretical modelling can be very useful to predict different properties of the compounds at hand or of correlated structures of increasing complexity, such as dendrons and dendrimers, giving a guide to the synthesis of (macro)molecules for applications in light-emitting and nonlinear optical devices, artificial light-harvesting systems or optical imaging of living tissues.

Hybrid Dendritic Molecules with Confined Chromophore Architecture to Tune Fluorescence Efficiency

The aim of this publication is to present a general strategy to engineer more efficient photoluminescent dendritic molecules based on polyhedral oligomeric silsesquioxane (POSS) cores. A series of chromophores were grafted on POSS cores to form dendritic molecules for which steric hindrance was used as a trigger to tune their photophysical properties. For fluorescence in the blue/near-UV spectral ranges, 4-vinylbiphenyl molecules were chosen as model chromophores to present a general approach based on stable chemistry and bulky groups grafted to the chromophores to enhance photoluminescence efficiency of the dendritic molecules. Photoluminescence quantum yields as well as steady-state and time-resolved solution spectroscopy along with molecular dynamics investigation and electronic structure calculations on a family of new materials are reported. We highlight an apparent contrast between free chromophore and dendritic molecules photophysical properties and show that chromophores' engineering and confinement around an inorganic core allows the design of more efficient photoluminescent dendritic molecules relevant to sensors and hybrid light-emitting diodes.

Synthesis, Characterization, Two‐Photon Absorption, and Optical Limiting Properties of Ladder‐Type Oligo‐p‐phenylene‐Cored Chromophores

AbstractThis paper reports on the two‐photon absorption (TPA) and related up‐converted emission properties of a novel series of chromophores containing ladder‐type oligo‐p‐phenylenes with various π‐conjugation lengths. The design and synthesis of these ladder‐type two‐photon chromophores are first discussed. An increase in the π‐conjugated length of the ladder‐type oligo‐p‐phenylene for these chromophores leads to an increase in TPA cross‐section together with an increased fluorescence quantum yield. These chromophores exhibit high fluorescence quantum yields because of the rigid planar structure of the ladder‐type oligomers. The chromophore with an enhanced TPA cross‐section together with an increased fluorescence quantum yield would provide significant benefits for two‐photon excited fluorescence based applications. An improved optical limiting behavior was also demonstrated using the ladder‐type pentaphenylene cored chromophore.

SYNTHESIS AND CHARACTERIZATION OF THIOPHENE-CONTAINING CHROMOPHORES FOR NONLINEAR OPTICAL (NLO) MATERIALS

A series of chromophores based on benzene and thiophene moieties as π-conjugating spacers were designed and synthesized by Horner-Emmons-Wadsworth reaction and Vilsmeier-Haack reaction, followed by Knoevenagel reaction with different electron acceptors. Their structures were confirmed by 1HNMR, FT-IR, HPLC-Ms, UV-visible spectra, and the thermal properties were characterized by differential scanning calorimetry (DSC). Solvatochromic method was used to measure their nonlinear optical properties. The variation of chromophoric structures on NLO properties was investigated, indicating that the cyano substitution on the vinylene bridge of the chromophore produces a considerable red-shift of the absorption maximum, and would greatly enhance the molecular quadratic hyperpolarizability (βμ).

Molecular Engineering of Intensely Near-Infrared Absorbing Excited States in Highly Conjugated Oligo(porphinato)zinc−(Polypyridyl)metal(II) Supermolecules

A new series of chromophores, MPZn(n), which combine ethyne-bridged bis(terpyridyl)metal(II)-(porphinato)zinc(II) (MPZ(n)) and oligomeric, ethyne-bridged (porphinato)zinc(II) (PZn(n)) architectures, have been synthesized and characterized, along with a series of derivatives bearing pyrrolidinyl electron-releasing groups on the ancillary terpyridine units (Pyr(m)MPZn(n)). Cyclic voltammetric studies, as well as NMR, electronic absorption, fluorescence, and femtosecond pump-probe transient absorption spectroscopies, have been employed to study the ground- and excited-state properties of these unusual chromophores. All of these species possess intensely absorbing excited states having large spectral bandwidth that penetrate deep in the near-infrared (NIR) energy regime. Electronic structural variation of the molecular framework shows that the excited-state absorption maximum can be extensively modulated [lambdamax(T(1) --> T(n))] (880 nm < lambdamax < 1126 nm), while concomitantly maintaining impressively large T(1) --> T(n) absorption manifold spectral bandwidth (full width at half-maximum, fwhm, approximately 2000-2500 cm(-1)). Furthermore, these studies enable correlation of supermolecular electronic structure with the magnitude of the excited-state lifetime (tau(es)) and demonstrate that this parameter can be modulated over 4 orders of magnitude ( approximately 1 ns < tau(es) < 45 micros). Terpyridyl pyrrolidinyl substituents can be utilized to destabilize terpyridyl ligand pi(*) energy levels and diminish the E1/2 (M3+/2+) value of the bis(terpyridyl)metal(II) center: such perturbations determine the relative energies of the PZn(n)-derived 1pi-pi(*) and bis(terpyridyl)metal(II) charge-transfer states and establish whether the T(1)-state wave functions of MPZn(n) and PyrmMPZn(n) species manifest the extensive electronic delocalization and charge-separated (CS) features characteristic of long-lived triplet states that absorb strongly in the NIR.

Modulated conjugation as a means for attaining a record high intrinsic hyperpolarizability

We report on a series of chromophores that have been synthesized with a modulated conjugation path between donor and acceptor. Hyper-Rayleigh scattering measurements of the best molecule show an enhanced intrinsic hyperpolarizability that breaches the apparent limit of all previously studied molecules.

Probing the Electronic Structure of Platinum(II) Chromophores: Crystal Structures, NMR Structures, and Photophysical Properties of Six New Bis- and Di- Phenolate/Thiolate Pt(II)Diimine Chromophores

A general route for synthesis of six structurally similar Pt(II) diimine thiolate/phenolates chromophores possessing bulky phenolate or thiolate ligands is reported. The Pt chromophores were characterized using an array of techniques including 1H, 13C, and 195Pt NMR, absorption, emission, (spectro)electrochemistry, and EPR spectroscopy. Systematic variation of the electronic structure of the Pt(II) chromophores studied was achieved by (i) changing solvent polarity; (ii) substituting oxygen for sulfur in the donor ligand; (iii) alternating donor ligands from bis- to di-coordination; and (iv) changing the electron donating/withdrawing properties of the ligand(s). The lowest excited state in these new chromophores was assigned to a [charge-transfer-to-diimine] transition from the HOMO of mixed Pt/S (or Pt/O) character on the basis of absorption and emission spectroscopy, UV/vis (spectro)electrochemistry, and EPR spectroscopy. One of the chromophores, Pt(dpphen)(3,5-di-tert-butyl-catecholate) represents an example of a Pt(II) diimine phenolate chromophore that possesses a reversible oxidation centered predominantly on the donor ligand. Results from EPR spectroscopy indicate participation of the Pt(II) orbitals in the HOMO. There is a dramatic difference in the photophysical properties of carborane complexes compared to other mixed-ligand Pt(II) compounds, which includes room-temperature emission and photostability. The charge-transfer character of the lowest excited state in this series of chromophores is maintained throughout. Moreover, the absorption and emission energies and the redox properties of the excited state can be significantly tuned.

Solvent effect on geometry and nonlinear optical response of conjugated organic molecules

AbstractIn this paper the effect of solvents of different polarity (chloroform and acetone) on the geometry and static electric properties (dipole moment, polarizability, and first hyperpolarizability) of four nonlinear optical (NLO) chromophores is studied within the framework of the Polarizable Continuum Model (PCM) at the Self‐consistent Field (SCF) level. The standard 6‐31G** basis set is used for the chromophore geometry optimization both in the gas phase and in the solvents, and a moderate‐size aug‐cc‐pVDZ* basis set is used for the calculation of electric properties of the chromophores under study. The effect of the solvent on the geometrical parameters of the chromophores is shown to be insignificant. However, to avoid inaccuracies in estimation of first hyperpolarizability, the use of chromophore geometries, optimized in a solvent, is recommended for chromophores with a rather long conjugation bridge between electron‐donating and electron‐withdrawing groups. The solvent effect on the calculated values of first hyperpolarizability results in its strong enhancement by a factor of 2.9–2.3 in the case of chloroform and by a factor of 3.9–2.8 in the case of acetone, the effect being somewhat attenuated with the lengthening of the conjugation bridge in the series of chromophores. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006

Synthesis and stability studies of conformationally locked 4-(diarylamino)aryl- and 4-(dialkylamino)phenyl-substituted second-order nonlinear optical polyene chromophores

A series of chromophores with high second-order nonlinearities has been synthesized; the chromphores consist of triarylamine or dialkylarylamine donors linked by a conformationally locked polyene bridge to a dicyanomethylidene acceptor. The use of bridges of this type, combined with the replacement of dialkylarylamine with triarylamine donors, leads to high thermal stability without adverse affects on the nonlinear optical properties of the chromophores.

Study on two-photon properties of a new series of chromophores

A new series of chromophores, styryl-quinolinium derivatives have been designed and synthesized. The linear absorption properties have been experimentally measured and the two-photon properties theoretically investigated on the basis of a quantum-chemical INDO/CI and the sum-over-states (SOS) method. The theoretical prediction for this group of derivatives shows that they have large two-photon absorption (TPA) cross sections as well as appropriate absorption wavelengths. The results show that the chromophores would be a kind of promising candidates of two-photon devices.

Photorefractive Properties of Poly(N-vinyl carbazole)-Based Composites for High-Speed Applications

The photorefractive properties of polymer composites based on poly(N-vinylcarbazole), doped with the sensitizer C60, the plasticizer butyl benzyl phthalate, and two series of chromophores are presented. The influence of the structure and the oxidation potential of the chromophore on the photorefractive properties is discussed. These materials show promise for video-rate optical processing applications, since they exhibit fast response times (beam-coupling growth times, τg, as small as 60 ms at 50 V/μm applied field and 200 mW/cm2 intensity and τg as small as 5 ms at 100 V/μm and 1 W/cm2).

Synthesis and Characterization of Highly Efficient, Chemically and Thermally Stable Chromophores with Chromone-Containing Electron Acceptors for NLO Applications

Donor–acceptor substituted nonlinear optical (NLO) chromophores possessing large molecular hyperpolarizabilities and chemical and thermal stabilities are of interest because of their potential applications in high-speed electro-optic devices. Here, a series of chromophores is presented with a diethylamino group as donor and a variety of strong electron withdrawing groups on the chromone moiety. Incorporation of these chromophores into a polyimide gives a material with high E-O coefficients, low optical loss, and good thermal stability.

Recent Progress of Electro-optic Polymers for Device Applications

AbstractElectro-optic (E-O) polymers have drawn great interest in recent years because of their potential applications in photonics devices such as high speed modulators and switches, optical data storage and information processing1–2. In order to have suitable materials for device fabrication, it is essential to design and develop polymeric material systems (active and passive polymers) with matched refractive indices, large E-O coefficients, good temporal and photochemical stability3–8 The E-O response of an active polymer commonly arises from the electric field induced alignment of its second-order nonlinear optical (NLO) chromophore, either doped as a guest/host system or covalently bonded as a side-chain. Because of the strong interaction among the electric dipoles, the poled structure is in a meta-stable state; the poled NLO chromophores which possess large dipole moment will tend to relax back to the randomly oriented state. As a result, the stability of the poled structure strongly depends on the rigidity of the overall material system. As it might be expected, the continuous increases of the rigidity and Tg of poled polymers imposes constraints on the selection of suitable chromophores that can survive the hightemperature poling and processing conditions. To circumvent this problem, we have developed a series of chromophores that possess conformation-locked geometry and perfluoro-dicyanovinylsubstituted electron-accepting group which demonstrate both good thermal stabilty and nonlinearity. This paper provides a brief review of these highly efficient and thermally stable chromophores and polymers for device applications.