In silico optimization of merocyanine-spiropyran compounds as second-order nonlinear optical molecular switches

Time-dependent Hartree-Fock and M?ller-Plesset second-order calculations have been used to unravel the relationships between structure and first hyperpolarizability in spiropyran/merocyanine couples and therefore to design efficient second-order nonlinear optical switching compounds. Large first hyperpolarizabilities for the merocyanine form as well as large contrasts of first hyperpolarizability have been obtained when, on the same species, (i) substituents at R(1) and R(2) positions on the phenolate ring of the merocyanine form are strong acceptor and donor substituents, respectively, (ii) the ethylenic bridge is substituted by donor groups, (iii) the other aromatic part of the system is benzimidazolo rather than indolino or benzothiazolo, and (iv) strong donor substituents are placed on the benzimidazolo moiety.     

Synthesis and spectral investigations of a new dyad with spiropyran and fluorescein units: toward information processing at the single molecular level

A new dyad 1 with two spiropyran units as the photochromic acceptors and one fluorescein unit as the fluorescent donor was synthesized and characterized. External inputs (ultraviolet light, visible light, and proton) induce the reversible changes of the structure and, concomitantly, the absorption spectrum of dyad 1 due to the presence of two spiropyran units. Only the absorption spectrum of the ME form of the spiropyran units in dyad 1 has large spectral overlap with the fluorescence spectrum of the fluorescein unit. Thus, the fluorescence intensity of dyad 1 is modulated by reversible conversion among the three states of the photochromic spiropyran units and the fluorescence resonance energy transfer (FRET) between the ME form and the fluorescein unit. Based on the fact that dyad 1 could "read out" three external input signals (ultraviolet light, visible ligh,t and proton) and "write" a compatible specific output signal (fluorescence intensity), dyad 1 described here can be considered to perform an integrated circuit function with one OR and one AND interconnected logic gates. The present results demonstrate an efficient strategy for elaborating and transmitting information at the single molecular level.     

含有Pt―Pt键金属配合物的电子结构和二阶非线性光学性质

采用量子化学密度泛函理论(DFT)结合有限场(FF)的方法对一系列含有Pt―Pt键金属配合物的电子结构和二阶非线性光学(NLO)性质进行了理论计算. 结果表明改变共轭配体对Pt―Pt键影响不大. 由配体到Pt―Pt金属基团的电荷转移强度随配体增长而变大. 金属配合物静态一阶超极化率随配体的增长而增大, 配合物电荷的改变基本不影响这类化合物的二阶NLO性质. 具有相对长的共轭配体的配合物IId具有最大的二阶NLO响应. 含时密度泛函理论(TD-DFT)计算表明配合物IId的二阶NLO响应来自于混有配体到金属的配体内的π→π^*电荷转移跃迁的贡献.     

Photochromic and reductive electrochemical switching of a dithiazolylethene with large redox modulation

A new dipyridylthiazolylethene (1a) and its dicationic analogue (2a), with two N-methylated pyridyl rings, have been synthesized and structurally characterized. Due to the N-methylation of the pyridyl rings, 2 a displays not only very different photochromic properties, but also undergoes a reductive ring-closing reaction to generate its closed-ring isomer 2b. Careful electrochemical studies coupled with EPR spectroscopy show that this reductive ring-closing reaction takes place when 2a is two-electron reduced. DFT calculations suggest that such a ground-state electrocyclization is driven by a very large stabilization of the reduced closed-ring isomer 2b relative to the reduced open-ring isomer 2a. In addition, 2b exhibits two successive and reversible one-electron reductions at half-wave potentials of 0.04 and -0.14 V versus SCE and a redox modulation as large as 1 V is achieved when passing from 2a to 2b.     

Photoresponsive n-channel organic field-effect transistors based on a tri-component active layer

Photoresponsive OFETs were fabricated based on a tri-component active layer (NDI2OD-DTYM2, spiropyran and polystyrene). The results demonstrated that these OFETs displayed photoresponsive feature to alternate UV and vis light due to the photoisomerization of spiropyran between the closed-ring state and ionic open-ring state.     

Multistate pi switches: synthesis and photochemistry of a molecule containing three switchable annelated dihydropyrene units

[structure: see text] The synthesis of the multistate photochromic switch 3 is described. This switch contains three dihydropyrene (DHP) units in the most conjugated fully closed form 3-c,c,c. The thermally stable form has the central DHP unit open and is 3-c,o,c. NMR and laser flash photolysis experiments were used to characterize the multiple states in the photoswitching of 3 by visible and UV light. Three of the possible five isomeric states of 3-c,o,c were observed. Irradiation of 3-c,o,c by visible light led to the formation of 3-o,o,o via the isomer 3-c,o,o as an intermediate, which were observed by NMR. Irradiation by UV light led to the formation of 3-c,c,c, which decays with a lifetime of 7.5 ms.     

Synthesis of 5'-Functionalized Indolinospiropyrans with Vinylene Unit as Linker

A protocol for the synthesis of a new family of spiropyran derivatives is described. A 5‐formylated indoline intermediate ( 5 ) was achieved for the first time, which was the key intermediate for constructing the spiropyran derivatives with vinylene linker. Five 5′‐functionalized indolinospiropyrans ( 11 – 15 ) were obtained by utilizing vinylene unit as a linkage between the photochromic spiropyran fragment and the ferrocene or triphenylamine donor.     

A sensitive sensor for Cu(II) based on a novel diarylethene with a bipyridyl moiety

A novel diarylethene with a bipyridyl unit has been designed and synthesized for the first time. Its photochromic behaviors could be modulated by protonation and coordination with Cu(II). The absorption maximum of the closed-ring isomer shifted from 569 to 666 nm when trifluoroacetic acid was added. Furthermore, the closed-ring isomer behaved as a sensitive colorimetric sensor, exhibiting an open-ring reaction upon exposure to Cu(II). Its high selectivity toward Cu(II) over other competitive species makes the ‘naked-eye’ detection of Cu(II) possible.     

Effective photoswitching of intramolecular magnetic interaction by diarylethene: Backgrounds and applications

Diarylethene is a photochromic molecule, which is potentially applicable to various optoelectronic devices. In diarylethenes the π-system of the two aryl rings is separated in the open-ring isomer, while the π-system is delocalized throughout the molecule in the closed-ring isomer. Based on this idea the exchange interaction between two nitronyl nitroxide radicals connected by a diarylethene unit was photocontrolled reversibly along with photochromism. The switching efficiency is more than 150-fold and thiophene spacer transmits the interaction more efficiently. When diarylethene dimer is used for the switching unit, the electric circuit-like behavior was observed. Moreover, reversed switching is achieved by reversing the thiophene ring. Magnetochemical and photochemical behavior of the radical-substituted diarylethene is described extensively.     

Quantum chemical study of redox-switchable second-order nonlinear optical responses of D-π-A system BNbpy and metal Pt(II) chelate complex

A second-order nonlinear optical (NLO) molecular switching with redox has been investigated in the present paper. The static first hyperpolarizabilities of 5-(BMes(2))-5'-(NPh(2))-2,2'-bipyridine (BNbpy) containing three-coordinate organoboron, Pt(II) chelate complex Pt(BNbpy)Ph(2), and their reduced forms have been calculated by density functional theory (DFT) combined with the analytic derivatives method. There is an enhancement of static first hyperpolarizabilities in the reduced form according to the calculations. That is, the β(vec) value of one-electron-reduced form is ~7 times as large as that of neutral form BNbpy; the β(vec) values of one- and two-electron-reduced forms are ~3 and ~4 times as large as that of neutral form Pt(BNbpy)Ph(2), respectively. In particular, the β(vec) value of two-electron-reduced form (3)Pt(BNbpy)Ph(2)(2-) is 1349 × 10(-30) esu, ~286 times larger than its neutral form. Moreover, the component β(z) value of the metal chelate complex Pt(BNbpy)Ph(2) is 25 × 10(-30) esu, which is ~14 times as large as that of ligand BNbpy; the corresponding F(-)/CN(-) compounds show a decrease in β(x) values compared with the case of the ligand and Pt(II) complex. Analyses of geometries, density of states (DOS), and time-dependent DFT (TDDFT) calculations reveal that the one-electron reduction promotes the molecular conjugation in the x-axis and intensifies the interaction between the metal Pt(II) and ligand and then results in an enhancement of the static first hyperpolarizability, whereas the binding of F(-)/CN(-) to the B atom turns off the p(π)-π* conjugation and has no effect on the conjugation of bipyridine, which leads to a decreasing β value in the x-axis.     

Spiropyran Photoswitches in the Context of DNA: Synthesis and Photochromic Properties

A new design is presented for the incorporation of spiropyran photoswitches into nucleic acids by oligonucleotide solid phase synthesis. This design enables interaction of the 6‐nitrospirobenzopyran (NitroBIPS) photoswitch with the adjacent nucleobases and leaves the photochemical properties of NitroBIPS intact. UV/Vis spectroscopy and HPLC revealed that NitroBIPS incorporated into DNA consists of up to 40 % merocyanine in its thermal equilibrium and undergoes reversible switching between the photoisomeric spiropyran (SP) and merocyanin (MC) state by alternating excitation using visible light or heat for at least fifteen switching cycles. Exchanging the chromene part of NitroBIPS on the DNA level gives access to differently substituted spiropyran derivatives allowing the screening for spiropyrans with suitable properties in a straightforward manner. Thus, by incorporating the highly hydrolysis‐stable pyrido‐spiropyran derivative PyBIPS pure light‐triggered reversible switching of a spiropyran in DNA has been realized for the first time. Therefore, this design represents a new useful platform for investigating the photochromic behavior of different spiropyran photoswitches in a nucleic acid environment and for using spiropyrans to induce light‐ or heat‐triggered changes in conformations or in fluorescence quenching properties of oligonucleotides.     

New photochromic 1,1,3-trimethylspiro[benzo[<Emphasis Type="Italic">e</Emphasis>]indoline-2,3′-[3<Emphasis Type="Italic">H</Emphasis>]-pyrano[3,2-<Emphasis Type="Italic">f</Emphasis>]quinoline]

A new photochromic spiropyran of the benzoindoline series containing the quinoline moiety was synthesized. Its structure was determined by IR and ¹H NMR spectroscopy. The crystal structure of the new compound was established by X-ray diffraction. The photochromic properties of the synthesized spiropyran were investigated.     

Theoretical study of the electronic and optical properties of photochromic dithienylethene derivatives connected to small gold clusters

In the course of developing electronic devices on a molecular scale, dithienylethenes photochromic molecules constitute promising candidates for optoelectronic applications such as memories and switches. There is thus a great interest to understand and control the switching behavior of photochromic compounds deposited on metallic surfaces or nanoparticles. Within the framework of the density functional theory, we studied the effect of small gold clusters (Au3 and Au9) on the electronic structure and absorption spectrum of a model dithienylethene molecule. The molecular orbital interactions between the photochromic molecule and the gold cluster made it possible to rationalize some experimental findings (Dulic, D.; van der Molen, S. J.; Kudernac, T.; Jonkman, H. T.; de Jong, J. J. D.; Bowden, T. N.; van Esch, J.; Feringa, B. L.; van Wees, B. J. Phys. Rev. Lett. 2003, 91, 207402). For the closed-ring isomer, grafting a photochromic molecule on a small gold cluster does not change the characteristics of the electronic transition involved in the ring-opening reaction. On the opposite, the absorption spectrum of the photochromic open-ring isomer is strongly modified by the inclusion of the metallic cluster. In agreement with experimental results, our study thus showed that the cycloreversion reaction which involves the closed-ring isomer should be still possible, whereas the ring-closure reaction which involves the open-ring isomer should be inhibited. Connecting a dithienylethene molecule to a small gold cluster hence provides a qualitative comprehension of the photochromic activities of dithienylethenes connected to a gold surface.     

Density Functional Theory Investigation on the Second‐Order Nonlinear Optical Properties of Chlorobenzyl‐o‐Carborane Derivatives

The structures and second‐order nonlinear optical (NLO) properties of a series of chlorobenzyl‐o‐carboranes derivatives ( 1 – 12 ) containing different push‐pull groups have been studied by density functional theory (DFT) calculation. Our theoretical calculations show that the static first hyperpolarizability (β_tot) values gradually increase with increasing the π‐conjugation length and the strength of electron donor group. Especially, compound 12 exhibits the largest β_tot (62.404×10^?30 esu) by introducing tetrathiafulvalene (TTF), which is about 76 times larger than that of compound 1 containing aryl. This means that the appropriate structural modification can substantially increase the first hyperpolarizabilities of the studied compounds. For the sake of understanding the origin of these large NLO responses, the frontier molecular orbitals (FMOs), electron density difference maps (EDDMs), orbital energy and electronic transition energy of the studied compounds are analyzed. According to the two‐state model, the lower transition energy plays an important role in increasing the first hyperpolarizability values. This study may evoke possible ways to design preferable NLO materials.     

十八烷基取代吲哚啉螺吡喃衍生物的合成及光谱性质

螺吡喃类化台物是一种重要的光响应分子,它在光信息存储技术中作为光盘材料具有广阔的应用前景。这类化合物在不同介质中的光谱、光电和光致变色性质引起了众多科学家的兴趣,并且已有大量研究工作报道。近年来,光致变色固体膜,特别是光致变色化合物的LB膜和超分子膜的特性引起了广泛的关注。因为在这种状态下,化合物分子具     

Recent developments in the field of metal complexes containing photochromic ligands: Modulation of linear and nonlinear optical properties

Organic photochromic molecules are important for the design of photoresponsive functional materials, as switches and memories. Over the past 10 years, research efforts have been directed towards the incorporation of photoresponsive molecules into metal systems, in order either to modulate the photochromic properties, or to photoregulate the redox, optical and magnetic properties of the organometallic moieties. This review article focuses on some of the recent work reported within the last few years in the area of organometallic and coordination complexes containing photochromic ligands for the photoregulation of optical and nonlinear optical properties. The first part is related to photochromic 1,2-diarylethene (DAE)-containing metal complexes, examples of mono- and multi-DAE metal-based will be discussed. The second part deals with metal complexes incorporating spiropyran and spirooxazine derivatives.     

TDDFT studies on chiral organophosphonate substituted divacant Keggin-type polyoxotungstate: diplex multistep-redox-triggered chiroptical and NLO switch

We theoretically investigate a novel switching phenomenon based on the divacant Keggin-type polyoxotungstate bearing chiral organophosphonate [{NH(2)CH(CH(3))PO}(2)(γ-SiW(10)O(36))](4-), that is the synchronous chiroptical and nonlinear optical (NLO) switch triggered by redox. The ECD calculations on the Boltzmann weighted conformations of the three oxidation states of this chiral polyoxometalate (POM) clearly present a chiroptical switching process. The electronic transition and the bond-length alternation studies show that the chirality transfer from chiral carbon atom to POM cage increases as the polyanion is reduced. Simultaneously, the static first hyperpolarizability of studied chiral POM quadrupled from the oxidized state to the 1e-reduced state, and is further doubled to the 2e-reduced state, which is mainly due to the increasing electronic-dipole-allowed d-d charge transfer transitions in the POM cage. This work firstly reproduces the ECD spectrum of chiral POM with high accuracy and proves the possibility for confirming the molecular conformations of flexible chiral POMs in solution by the aid of ECD calculations. Most importantly, a sensitive diplex switch based on a chiral POM is predicted in theory, which may aid the design of novel POM-based switches.     

Photo-and thermochromic spiranes. 29. New photochromic indolinospiropyrans containing a quinoline fragment

A new photochromic spiropyran of the indoline series, containing a quinoline fragment, has been synthesized. The photochromic properties of the spiropyran and its iodomethylate have been studied. Features of the molecular structure of the compounds were determined by X-ray structural investigations. It was established that the pyridopyran fragments of the cations in the crystal of the iodomethylate salt, unlike those in the crystal of the neutral spiropyran, emerge from 2₁-stacks, disposed jointly with I⁻ ions, which causes their higher mobility and aids the course of reversible photoconversions on UV irradiation in solution. For Part 28 see [1]. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 690–702, May, 2007.     

Preparation and properties of photochromic bacterial cellulose nanofibrous membranes

The photochromic bacterial cellulose (BC) nanofibrous membranes containing 1′,3′,3′-trimethyl-6-nitrospiro(2H-1-benzopyran-2,2′-indoline) (NO₂SP) were successfully prepared by surface modification of BC nanofibers with spiropyran photochromes, and their physical and photochromic properties were characterized. The FTIR spectra indicated the interaction between BC and NO₂SP which leads to the uniform dispersion of NO₂SP in the nanofibrous membrane. SEM results demonstrated that the introduction of NO₂SP maintains the nanofibrous network structure of BC. UV/vis spectrometry of the resulting BC-NO₂SP revealed that the membranes show reversible photochromic property by changing their color from colorless to pink forming a merocyanine structure upon UV irradiation, and returning back again to colorless spiropyran structure by visible light. The contact angle of the BC-NO₂SP with water was found to be reversibly regulated due to the reversible isomerization of the spiropyran moieties in BC-NO₂SP. The result indicates that the surface modification with spiropyran photochromes expands new applications of BC nanofibers and such photochromic nanofibers with excellent photosensitivity have great potentials for sensitive displays, biosensors and other optical devices.     

Synthesis and Photochromic Properties of the Derivatives of Spiropyrans Containing a Mesogenic Group

The photochromic compounds continue to attract significant attention in view of their general applicability as optical information storage materials or switching devices1-2.In order to develop novel bifunctional and multifunctional materials,special attention has been paid to photochromic liquid crystalline compounds.Many studies have been carried out for all kinds of mixed systems,which are to dope small amounts photochromic compounds into liquid crystal3-4.However,the combination of the prop…