Selective Acceleration of the Protonated Merocyanine‐Spiropyran Photochromic Transformation by Inclusion in Cucurbit[7]uril

The effect of cucurbit[7]uril (CB7) on the spiropyran‐merocyanine photochromic interconversion was studied in acidic and alkaline aqueous solutions. The merocyanine (MC) isomer was found to be the thermodynamically most stable form both in water and in the presence of CB7. A preferential binding of the protonated merocyanine (MCH⁺) to CB7 was observed with an equilibrium constant of 7.4 × 10⁴ m ^?1, and the complex formation led to significant diminution of acidity of the guest. The photoinduced transformation of MCH⁺ to the spiropyran isomer was accelerated 2.3‐fold upon addition of CB7, whereas the rates of the other photochromic processes were not affected. The partial inclusion of MCH⁺ in CB7 led to dual fluorescence due to the incomplete deprotonation in the singlet‐excited state.     

Thermolysis of hexasubstituted‐4,5‐dihydro‐3H‐pyrazoles: Kinetics and activation parameters

A kinetics study of the thermolysis of a series of hexasubstituted‐4,5‐dihydro‐3H‐pyrazoles (pyrazolines 1a: 3,3,4,4‐tetramethyl‐5‐phenyl‐5‐acetoxy; 1b: cis‐3,5‐diphenyl‐3,3,4‐trimethyl‐5‐acetoxy; 1c: cis‐3,5‐diphenyl‐3,4,4‐trimethyl‐5‐methoxy; 1d: 3,3,5‐triphenyl‐4,4‐dimethyl‐5‐acetoxy), which produced the corresponding hexasubstituted cyclopropanes 2a–d in quantitative yields was carried out. The first order rate constants (k₁) for thermal decomposition and activation parameters were determined. The relative reactivity series was found to be 1d >> 1b ∼ 1c > 1a. The activation parameters for thermolysis were found to be: for 1a ΔH‡ = 39.8 kcal/mol, ΔS‡ = 14 eu, k_150° = 6.8 × 10⁻⁵ s⁻¹; for 1b ΔH‡ = 33.5 kcal/mol, ΔS ‡ = 0.2 eu, k_150° = 1.7 × 10⁻⁴s⁻¹; for 1c ΔH‡ = 32.7 kcal/mol, ΔS‡ = −1.8 eu, k_150° = 1.2 × 10⁻⁴s⁻¹; for 1d ΔH‡ = 30.1 kcal/mol, ΔS‡ = −1.6 eu, k_150° = 8.8 × 10⁻³s⁻¹. The effect of variation of C3 substituents on the activation parameters for thermolysis paralleled the trend reported for acyclic analogs. The results are consistent with the formation of a (singlet) 1,3‐diradical intermediate with subsequent closure to yield the cyclopropanes. The mechanism of diradical formation appears to involve N₂‐C₃ bond cleavage as the rate determining step rather than simultaneous two bond scission. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:299–302, 2000     

Sensitivity and Resolution Development of Spiropyran‐based Molecular Photoswitches

The phenylazo moiety and its donor‐ and acceptor‐substituted derivatives are studied as effective auxochromes to improve their sensitivity and resolution for distinguishing between the spiro (SP; OFF) and mero (ON) forms in molecular photoswitching applications. Thus, 13 azospiropyran derivatives were synthesized and their spectroscopic and photokinetic behaviors were studied. The quality of photochromic reactions of the synthesized photochromic compounds were compared using a dose–response model. Interestingly, by replacing the nitro group in 6‐nitrospiropyran (ε = 0.42 × 10⁴ M^?1 cm^?1) with a simple phenylazo moiety, the SP form is still colorless and the color intensity of the merocyanine (MC) form is improved desirably by extending the conjugation length ( 1a , ε = 1.35 × 10⁴ M^?1 cm^?1). The presence of a hydrophilic OH group or a CH₃ group at the para position of phenylazo moiety revealed more or less the same photochromic properties as 1a . The OCH₃ group substituted at position 6 of the phenylazo moiety at the para position of the azobenzene moiety effectively increased the photochromic properties with the maximum k‐value for SP to MC switching. Meanwhile, Cl, Br, COOH, and NO₂ groups at the para position of the azobenzene moiety revealed the reduction in photochromic properties compared to 1a .     

Synthesis and Photochromic Behaviour of Novel 2H‐1‐Benzopyrans (=2H‐Chromenes) Derived from Carbazololes

The synthesis and photochromic properties of new 2,2‐diphenyl‐2H‐1‐benzopyrans, fused to an indole moiety, are described. All compounds exhibit photochromic behaviour in solution at room temperature. The heteroanellation effects are variable and depend on the position and geometry of the fused indole moiety. A general bathochromic shift in the spectra of the open forms is observed. The presence of a N‐methyl group prevents the broadening of the absorption spectra and promotes the instability of some photoinduced forms of compounds with the indole moiety fused at the 5,6 positions of the 2H‐1‐benzopyran skeleton. The enhanced photocolouration efficiency in the near‐UV and the kinetics of thermal bleaching indicate that the novel compounds with an indole moiety fused at the 6,7 positions, particularly those with a linked thiophene moiety, are very interesting molecules for applications in the field of variable optical absorption systems.     

Studies under Continuous Irradiation of Photochromic Spiro[fluorenopyran‐thioxanthenes]

New indeno‐fused spiro[benzopyran‐thioxanthenes] were synthesized (see 3a – d in Scheme 3) and their photochromic properties evaluated under continuous irradiation (Table 1). When submitted to irradiation for several minutes with a Xe lamp, the system behaved as one constituted by two open colored forms with different thermal bleaching rates and different susceptibilities to degradation. An increase in irradiation time led to significant degradation and to the apparent predominance of the open colored form with the faster bleaching rate.     

The synthesis and cytotoxic evaluation of a series of benzodioxole substituted titanocenes

Using 6‐benzo[1,3]dioxolefulvene ( 1a ), a series of benzodioxole substituted titanocenes was synthesized. The benzyl‐substituted titanocene bis[(benzo[1,3]dioxole)‐5‐methylcyclopentadienyl] titanium (IV) dichloride ( 2a ) was synthesized from the reaction of Super Hydride with 1a . An X‐ray determined crystal structure was obtained for 2a . The ansa‐titanocene {1,2‐di(cyclopentadienyl)‐1,2‐di‐(benzo[1,3]dioxole)‐ethanediyl} titanium(IV) dichloride ( 2b ) was synthesized by reductive dimerisation of 1a with titanium dichloride. The diarylmethyl substituted titanocene bis(di‐(benzo[1,3]dioxole)‐5‐methylcyclopentadienyl) titanium(IV) dichloride ( 2c ) was synthesized by reacting 1a with the para‐lithiated benzodioxole followed by transmetallation with titanium tetrachloride. When titanocenes 2a–c were tested against pig kidney (LLC‐PK) cells inhibitory concentrations (IC₅₀) of 2.8 × 10^?4, 1.6 × 10^?4 and 7.6 × 10^?5 M , respectively, were observed. These values represent improved cytotoxicity against LLC‐PK, when compared with unsubstituted titanocene dichloride, but are not as impressive as values obtained for titanocenes previously synthesized using the above methods. Copyright © 2006 John Wiley & Sons, Ltd.     

DFT/TDDFT Investigation of the Modulation of Photochromic Properties in an Organoboron‐Based Diarylethene by Fluoride Ions

The diarylethene derivative 1,2‐bis‐(5′‐dimesitylboryl‐2′‐methylthieny‐3′‐yl)‐cyclopentene ( 1 ) containing dimesitylboryl groups is an interesting photochromic material. The dimesitylboryl groups can bind to F^?, which tunes the optical and electronic properties of the diarylethene compound. Hence, the diarylethene derivative 1 containing dimesitylboryl groups is sensitive to both light and F^?, and its photochromic properties can be tuned by a fluoride ion. Herein, we studied the substituent effect of dimesitylboron groups on the optical properties of both the closed‐ring and open‐ring isomers of the diarylethene molecule by DFT/TDDFT calculations and found that these methods are reliable for the determination of the lowest singlet excitation energies of diarylethene compounds. The introduction of dimesitylboron groups to the diarylethene compound can elongate its conjugation length and change the excited‐state properties from π→π* transition to a charge‐transfer state. This explains the modulation of photochromic properties through the introduction of dimesitylboron groups. Furthermore, the photochromic properties can be tuned through the binding of F^? to a boron center and the excited state of the diarylethene compound is changed from a charge‐transfer state to a π→π* transition. Hence, a subtle control of the photochromic spectroscopic properties was realized. In addition, the changes of electronic characteristics by the isomerization reaction of diarylethene compounds were also investigated with theoretical calculations. For the model compound 2 without dimesitylboryl groups, the closed‐ring isomer has better hole‐ and electron‐injection abilities, as well as higher charge‐transport rates, than the open‐ring isomer. The introduction of dimesitylboron groups to diarylethene can dramatically improve the charge‐injection and ‐transport abilities. The closed isomer of compound 1 ( 1 C ) has the best hole‐ and electron‐injection abilities, whereas the charge‐transport rates of the open isomer of compound 1 ( 1 O ) are higher than those of 1 C . Importantly, 1 O is an electron‐accepting and ‐transport material. These results show that the diarylethene compound containing dimesitylboryl groups has promising potential to be applied in optoelectronic devices and thus is worth to be further investigated.     

Synthesis,Characterization and Photochromic Properties of Novel Naphthopyrans with Hydrazone Unit Residue

A series of naphthopyrans with hydrazone unit ( 8a – 8m ), were synthesized and characterized by ¹H NMR, ¹³C NMR, IR and HRMS. The photochromic properties were investigated under continuous irradiation, in particular regard to the fatigue resistance and the lifetime of the colored open form in solution and polymers. The results showed that these compounds had both good photochromic properties and high fatigue resistance. Detailed studies showed that representative compound 8d (3,3‐di‐4‐methoxybenzoic acid methylenehydrazino‐[3H]‐naphtho [2,1‐b]pyran) had good photochromic properties in THF solution, in solid state, and in polymers, and exhibited a significant bathochromic shift in the spectra of the open forms compared to known naphthopyrans 9 (3,3‐diphenyl‐[3H]‐naphtho[2,1‐b]pyran). On the other hand, the higher melting points of target compounds are promising for the polymer film preparation through hot‐melt method.     

Preparation of polymers having hole and electron transport units by Friedel–Crafts reaction

Polymers having 2,5‐diphenyl‐1,3,4‐oxadiazole (BCO) or anthracene (BCA) as an electron transport unit and N,N′‐diphenyl‐N,N′‐bis(4‐butylphenyl)‐benzidine (BTPD) as a hole transport unit were prepared by condensation polymerization using Friedel–Crafts reaction. It was found that BCO was less reactive than BCA. The low reactivity of the BCO monomer can be explained by the oxygen atom in the oxadiazole unit, which acts as a Lewis base and reduces the activity of the catalyst. The redox behavior measured by cyclic voltammetry showed for both BTPD‐BCO and BTPD‐BCA almost the same oxidation potential. In addition, the BTPD‐BCO also exhibited a reduction peak. Hole and electron drifts mobility of the polymers were measured by the time‐of‐flight method. The hole drift mobility of both BTPD‐BCO and BTPD‐BCA was 7.4 × 10^?5 cm² V^?1 s^?1. The electron drift mobilities of BTPD‐BCO and BTPD‐BCA were 6.5 × 10^?5 cm² V^?1 s^?1 and 5.2 × 10^?6 cm² V^?1 s^?1, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3083–3089, 2007     

Synthesis and nonlinear optical properties of polyester containing 4‐di‐(2′‐hydroxyethoxy)‐4‐diphenyl‐hydrazonomethyl chromophore

The nonlinear optical property of new polyester has been studied via second harmonic generation (SHG). The values of electro‐optic coefficients, d₃₃ and d₃₁, of the poled polymer film were 3.15 × 10 ^?7 and 1.5 × 10^?7 esu, respectively. Thermal behavior of this polyester was studied through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). 4‐di‐(2′‐hydroxyethoxy)‐4‐diphenyl‐hydrazonomethyl was synthesized from the reaction of 3,4‐dihydroxy‐4‐diphenyl‐hydrazonomethyl with 2–chloro–1‐ethanol in a 1:2 mole ratio and subsequently reacted with terephthaloyl chloride (TPC) in the presence of pyridine, as catalyst, to produce the new nonlinear polyester. The chemical structures of the resulting monomers and polymer were characterized by CHN analysis, ¹H‐NMR, FT‐IR, and UV–Vis spectroscopy. Copyright © 2009 John Wiley & Sons, Ltd.     

Manufacture and demonstration of organic photovoltaic‐powered electrochromic displays using roll coating methods and printable electrolytes

Electrochromic devices (ECDs) were prepared on flexible substrates using spray coating and slot‐die coating methods. The electrochromic materials were the conjugated electroactive polymers, poly((2,2‐bis(2‐ethylhexyloxymethyl)‐propylene‐1,3‐dioxy)‐3,4‐thiophene‐2,5‐diyl) as a vibrantly colored active material (ECP‐Magenta) and poly(N‐octadecyl‐(propylene‐1,3‐dioxy)‐3,4‐pyrrole‐2,5‐diyl) as a minimally colored, charge balancing material (MCCP). Two electrolyte systems were compared to allow development of fully printable and laminated devices on flexible substrates. Devices of various sizes, up to 7 × 8 cm², are demonstrated with pixelated devices containing pixel sizes of 4 × 4 mm² or 13 × 13 mm². The transmission contrast exhibited by the devices, when switched between the fully bleached and fully colored state, was 58% at a visible wavelength of 550 nm, and the devices exhibited switching times of <10 s. Additionally, we demonstrate the utilization of printed organic photovoltaic devices (with or without the use of a lithium‐polymer battery) to power the devices between the colored and bleached state, illustrating a self‐powered ECD. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

New class of cationic ring‐opening polymerizations of 2,2‐diphenyl‐1,3‐oxathiolanes accompanying quantitative elimination of benzophenone

Cationic polymerizations of three 2‐substituted 1,3‐oxathiolanes, 2,2‐diphenyl‐1,3‐oxathiolane ( 1a ), 5‐methyl‐2,2‐diphenyl‐1,3‐oxathiolane ( 1b ), and 4‐methyl‐2,2‐diphenyl‐1,3‐oxathiolane ( 1c ), were carried out with boron trifluoride etherate (BF₃ · OEt₂) in dichloromethane at 30 °C to obtain poly(alkylene sulfide)s accompanying the elimination of benzophenone. In the cationic polymerization of 1b and 1c , the consumption of the monomers and formation of benzophenone proceeded simultaneously. The obtained poly(propylene sulfide)s from 1b and 1c contain 41% head–head units, which is in good agreement with that of the polymer from methylthiirane with BF₃ · OEt₂. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2943–2949, 2004     

Dehydration Kinetics of Zinc Phosphate Tetrahydrate α-Zn3（PO4）2·4H2O Nanoparticle

TG-DTG technique and Harcourt-Esson integrated equation were used to study the dehydration process of zinc phosphate tetrahydrate α-Zn3（PO4）2·4H2O nanoparticle and its thermal decomposition kinetics. The results show that there are three stages of dehydration between 300 and 800 K during the thermal decomposition of α-Zn3（PO4）2·4H2O nanoparticle. The first stage is controlled by chemical reaction with an activation energy of 69.48 kJ·mol^-1 and a pre-exponential factor of 1.77×10^6 s^-1. The second is controlled by nucleation and growth with an activation energy of 78.74 kJ·mol^-1 and a pre-exponential factor of 5.86×10^9 s^-1. The third is controlled by nucleation and growth with an activation energy of 141.5 kJ·mol^-1 and a pre-exponential factor of 1.01×10^12 s^-1. The kinetic compensative effects not only exist in Arrhenius equation but also in Harcourt-Esson equation. Activation energy E is dependent on both the decomposition fraction α and temperature T.     

Kinetics of the mercury(II)‐catalyzed substitution of coordinated cyanide ion in hexacyanoruthenate(II) by nitroso‐R‐salt

The kinetics and mechanism of Hg²⁺‐catalyzed substitution of cyanide ion in an octahedral hexacyanoruthenate(II) complex by nitroso‐R‐salt have been studied spectrophotometrically at 525 nm (λ_max of the purple‐red–colored complex). The reaction conditions were: temperature = 45.0 ± 0.1°C, pH = 7.00 ± 0.02, and ionic strength (I) = 0.1 M (KCl). The reaction exhibited a first‐order dependence on [nitroso‐R‐salt] and a variable order dependence on [Ru(CN)₆^4?]. The initial rates were obtained from slopes of absorbance versus time plots. The rate of reaction was found to initially increase linearly with [nitroso‐R‐salt], and finally decrease at [nitroso‐R‐salt] = 3.50 × 10^?4 M. The effects of variation of pH, ionic strength, concentration of catalyst, and temperature on the reaction rate were also studied and explained in detail. The values of k₂ and activation parameters for catalyzed reaction were found to be 7.68 × 10^?4 s^?1 and E_a = 49.56 ± 0.091 kJ mol^?1, ΔH^≠ = 46.91 ± 0.036 kJ mol^?1, ΔS^≠ = ?234.13 ± 1.12 J K^?1 mol^?1, respectively. These activation parameters along with other experimental observations supported the solvent assisted interchange dissociative (I_d) mechanism for the reaction. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 215–226, 2009     

Kinetics of the reaction of O3 with selected benzenediols

The kinetics of the reaction of O₃ with the aromatic vicinal diols 1,2‐benzenediol, 3‐methyl‐1,2‐benzenediol, and 4‐methyl‐1,2‐benzenediol have been investigated using a relative rate technique. The rate coefficients were determined in a 1080‐L smog chamber at 298 K and 1 atm total pressure of synthetic air using propene and 1,3‐butadiene as reference compounds. The following O₃ reaction rate coefficients (in units of cm³ molecule^?1 s^?1) have been obtained: k(1,2‐benzenediol) = (9.60 ± 1.12) × 10^?18, k(3‐methyl‐1,2‐benzenediol) = (2.81 ± 0.23) × 10^?17, k(4‐methyl‐1,2‐benzenediol) = (2.63 ± 0.34) × 10^?17. Absolute measurements of the O₃ rate coefficient have also been carried out by measuring the decay of the dihydroxy compound in an excess of O₃. The results from these experiments are in good agreement with the relative determinations. Atmospheric implications are discussed. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 223–230, 2003     

Lewis Acid Modulation in a Amido-functional Diarylethene and Its Hypsochromism Effect

A photochromic diarylethene,1,2-bis(2-methyl-5-(4-N,N-dimethylaminophenyl)thien-3-yl)perfluorocyclopen-tene in proton-donating media was studied.The ammonium salt came into being in the presence of acetic acidfollowing localization of lone pair electrons of the amino group.The maximum absorption of the salt had a 36 nmhypsochromic shift,and its molar extinction coefficient increased to 3.494×10~4 L·mol~(-1)·cm~(-1).The conjugationaland delocalizational energy levels were calculated by Gaussian 98,and its hypsochromic shift mechanism was alsodiscussed.     

Photochromic benzo[<Emphasis Type="Italic">g</Emphasis>]indolyl fulgimide with modulated fluorescence

A new photochromic fulgimide, (E)-1-(anthracen-9-ylmethyl)-3-[1-(5-methoxy-2-methyl-1-phenyl-1H-benzo[g]indol-3-yl)ethylidene]-4-(propan-2-ylidene)pyrrolidine-2,5-dione, has been synthesized and found to exhibit fluorescence. The structure of this compound and intermediate fulgenates and amidofulgenic and fulgenic acids has been determined by electronic and vibrational spectroscopy, ¹H and ¹³C NMR, and mass spectrometry. The amidofulgenic and fulgenic acids are capable of undergoing photoinduced reversible Z/E isomerization with respect to the C=C bond without subsequent cyclization, whereas fulgenates are converted to the corresponding cyclic structures. The new fluorescent fulgimide is transformed into the colored nonfluorescing cyclic isomer under UV irradiation. The reverse ring opening under visible light irradiation restores the fluorescence properties, which makes this compound a molecular fluorescence switch.     

Photoinduced electron transfer of [ Ru (bpy)_2 (4, 4'-dcbpy)]~(2 ) with electron donors

Emission quenching of [Ru(bpy)2(4, 4'-dcbpy)] (PF6)2 (1) by benzenamine,4-[2-[5-[4-[4-dimethylamino]phenyl]-4,5-di-hydro-1-phenyl-1H-pyrazol-3-yl]-ethenyl]-N,N-dimetyl (2) or 1, 5-diphenyl-3-(2-phenothiazine)-2-pyrazoline (3) was observed. Measurements of the emission decay of 1 before and after addition of 2 or 3 by single photon counting technique con-finned the observations. The emission quenching of 1 by 2 or 3 was submitted to Stern-Volmer equation. It was calculated that the quenching rate constants (kq) are 5.5 × 109(mol/L)-1s-1 for 2 and 4.0 × 109(mol/L)-1s-1 for 3, respectively. These results indicated a character of dynamic quenching process. The singlet-state of 2 or 3 was also quenched by 1. The quenching behaviors did not conform to the Stern- Volmer equation and involved both static and dynamic quenching processes. The apparent quenching rate constant (kapp) was calculated to be 3 × 109 (mol/L)-1 for the interaction of excited 2 with 1, and 1.2 × 109 (mol/L)-1 for that of excited 3 wit     

Differential Detection of Zn2+ and Cd2+ Ions by BODIPY‐Based Fluorescent Sensors

Two monostyryl BODIPY derivatives that contain one or two bis(hydroxyamido)amino group(s) as the metal chelator have been prepared. The effects of various metal ions on their electronic absorption and fluorescence properties have been studied in detail in MeCN or in phosphate buffered saline (PBS). The results show that the derivative with two hydroxyamide chains can selectively detect Zn²⁺ ions in MeCN. The compound and ions bind in a 1:1 stoichiometry with an association constant of 2.2(±0.1)×10⁴ M ^?1. The intensity of the fluorescence emission increases remarkably and is substantially blue‐shifted from 624 to 572 nm, owing to the inhibition of intramolecular charge transfer, thus allowing its use as a ratiometric fluorescent sensor for Zn²⁺ ions. The derivative with four hydroxyamide chains behaves differently: It responds selectively toward Cd²⁺ ions in phosphate buffered saline. The compound and ions bind in a 1:2 stoichiometry, with first and second association constants of 4.4(±0.9)×10⁴ M ^?1 and 1.3(±0.1)×10⁴ M ^?1, respectively. Upon the addition of 80 equivalents of Cd²⁺ ions, the fluorescence quantum yield increases 15‐fold. Both of these compounds exhibit differential sensing of Zn²⁺ and Cd²⁺ ions and the associated color changes can be easily seen by the naked eye.     

DNA binding and nuclease activity of cationic iron(IV) and manganese(III) corrole complexes

Cationic meso(4‐N‐methylpyridyl)‐based metallocorroles, μ‐oxo iron corrole dimer ( 1b ) and manganese corrole monomer ( 2b ), were synthesized and characterized. The interactions of these two metal corrole complexes with CT‐DNA were studied by UV–visible, fluorescence and circular dichroism spectroscopic methods, as well as by viscosity measurements. The results revealed that 1b interacts with CT‐DNA in a difunctional binding mode, i.e. non‐classical intercalation and outside groove binding with H‐aggregation, while 2b can interact with CT‐DNA via an outside groove binding mode only. The binding constants K_b of 1b and 2b were 4.71 × 10⁵ m ^?1 and 2.17 × 10⁵ m ^?1, respectively, indicating that 1b can bind more tightly to CT‐DNA than 2b . Furthermore, both complexes may cleave the supercoiled plasmid DNA efficiently in the presence of hydrogen peroxide or tert‐butyl hydroperoxide (TBHP), albeit 1b exhibited a little higher efficiency. The inhibitor tests suggested that singlet oxygen and high‐valent (oxo)iron(VI) corrole or (oxo)manganese(V) corrole might be the active intermediates responsible for the oxidative DNA scission. Copyright © 2014 John Wiley & Sons, Ltd.