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Richard A Evans - One of the best experts on this subject based on the ideXlab platform.
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photochromic polymer conjugates the importance of macromolecular architecture in controlling switching speed within a polymer matrix
Macromolecules, 2010Co-Authors: Francesca Ercole, Thomas P Davis, Nino Malic, Simon Harrisson, Richard A EvansAbstract:Naphthopyran−poly(n-butyl acrylate) conjugates with different geometries were assembled using ATRP. First, within a rigid lens matrix, an investigation of the photochromic behavior of various poly(n-butyl acrylate), p(n-BA), homopolymers showed that midplacement of a single dye moiety, made possible using a Y-branching difunctional photochromic initiator, gave superior fade kinetics per chain length of conjugated polymer compared to end-functionalized homopolymers. Furthermore, having the dye pendant from the chain opposed to directly within the chain was also found to be advantageous. Fading kinetics became faster when chain length was increased, except in the case of linear random copolymers made by copolymerization of n-butyl acrylate with a Naphthopyran acrylate. A gradient copolymer made with a nonphotochromic difunctional initiator and a Naphthopyran methacrylate displayed superior kinetics. Films consisting of ABA triblock copolymers, incorporating the photochromic in the middle of a soft p(n-BA) s...
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comprehensive modulation of Naphthopyran photochromism in a rigid host matrix by applying polymer conjugation
Macromolecules, 2009Co-Authors: Francesca Ercole, Thomas P Davis, Richard A EvansAbstract:Naphthopyran polymer conjugates of various rigidities were synthesized by atom transfer radical polymerization (ATRP), and their photochromic properties were tested within a rigid host matrix. Broad tuning of photochromic kinetics was displayed as a result of polymer conjugation because of its ability to alter the local environment of the Naphthopyran within the host. End-functionalized conjugates, synthesized from a Naphthopyran-functionalized ATRP initiator, allowed systematic tuning of kinetics via modulation of chain length of attached polymer. Reducing the rigidity of the conjugate resulted in an acceleration of kinetics and an increase in colorability. Pronounced chain lengths of poly(methyl methacrylate) (>18 000 g/mol) were required for decoloration kinetics to be effectively depressed compared with an unconjugated Naphthopyran control. Random in-chain incorporation of the Naphthopyran was afforded by copolymers made with Naphthopyran-functionalized monomers. At the expense of a defined placement ...
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superior photochromic performance of Naphthopyrans in a rigid host matrix using polymer conjugation fast dark and tunable
Macromolecules, 2008Co-Authors: Nino Malic, Jonathan A Campbell, Richard A EvansAbstract:The attachment of low Tg poly(n-butyl acrylate) polymers (Mn 4100 to 13 100) to Naphthopyran photochromic dyes provided large tunable improvements in their photochromic performance in a rigid thermoset host polymer matrix. Both coloration and decoloration speeds were greatly increased, with the critical t1/2 decoloration times reduced by 50−95% and t3/4 decoloration times reduced by at least 63% through the use of these polymer conjugates. In addition, the optical density of the colored form of the dye−polymer conjugates rapidly reached a steady state absorption ca. 60−70% greater than the nonpolymer conjugated control dyes. The effect of the geometry of the polymer conjugates was examined, and it was found that mid-placement of the dye on the polymer provided secondary decoloration speed enhancement over end-placement. Thus, conjugation of low Tg poly(n-butyl acrylate) not only provides faster coloration and decoloration but also greatly increases optical density with near square-wave characteristics.
Heron B. Mark - One of the best experts on this subject based on the ideXlab platform.
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Quenching of the phosphorescence of thermally reversible photochromic Naphthopyran Re( i ) complexes initiated by either visible or ultraviolet radiation
'Royal Society of Chemistry (RSC)', 2021Co-Authors: De Azevedo Orlando, Heron B. Mark, Elliott Paul, Gabbutt Christopher, Jacquemin Denis, Rice Craig, Scattergood PaulAbstract:International audienceRe(i) complexes bearing thermally reversible photochromic Naphthopyran axial ligands undergo highly efficient, reversible phosphorescence quenching actuated by either visible or UV irradiation. The photoinduced quenching of the triplet metal-to-ligand charge-transfer (3MLCT) emission is interpreted based on changes in the relative energies of the excited states
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Processing Binary and Fuzzy Logic by Chaotic Time Series Generated by a Hydrodynamic Photochemical Oscillator
'Wiley', 2017Co-Authors: Gentili, Pier Luigi, Giubila, Maria S., Heron B. MarkAbstract:This work demonstrates the computational power of a hydrodynamic photochemical oscillator based on a photochromic Naphthopyran generating aperiodic time series. The chaotic character of the time series is tested by calculating its largest Lyapunov exponent and the correlation dimension of its attractor after building its phase space through the Takens’ theorem. Then, the chaotic dynamic is shown to be suitable to implement all the fundamental Boolean two-inputs-one-output logic gates. Finally, the strategy to implement fuzzy logic systems (FLSs) based on the time series is described. Such FLSs promise to be useful in the field of computational linguistics, which is concerned with the development of artificial intelligent systems able to transform collections of numerical data into natural language texts
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Photochromic bi-Naphthopyrans
'Elsevier BV', 2015Co-Authors: Aiken Stuart, Gabbutt, Christopher D., Heron B. Mark, Kolla, Suresh B.Abstract:A series of novel 3-aryl-(3,3-diaryl-3H-naphtho[2,1-b]pyran-8-yl)-3H-naphtho[2,1-b]pyrans has been accessed from 6-bromo-2-naphthol via a four step transformation. Acylation of the dianion derived from the treatment of 6-bromo-2-naphthol with n-butyllithium with Weinreb amides and subsequent reaction with a 1,1,-diarylprop-2-yn-1-ol gave 8-aroyl-3H-naphtho[2,1-b]pyrans in good yield. Addition of lithium trimethylsilylacetylide to the foregoing 8-aroylNaphthopyrans proceeded smoothly with base mediated desilyation to afford the target bi-Naphthopyrans upon acid-catalysed reaction with 2- naphthol. Preliminary evaluation of the photochromic response of the new bi-Naphthopyrans revealed reversible independent Naphthopyran ring-opening leading to a complex photochromic signature
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Merocyanine Dyes and Photochromic Naphthopyrans
Proteomass Scientific Society (Portugal), 2014Co-Authors: Heron B. MarkAbstract:DiarylNaphthopyrans 1 and 2 have been widely used as the photochromic component in commercial ophthalmic sun lenses. Through the careful choice of dye structure and polymer matrix the color and persistence of the photomerocyanine dyes 3 and 4 can be controlled (Scheme 1). The use of photochromic dyes to modulate various phenomena, including fluorescence, has developed into an attractive research area. We have previously reported on the influence of the UV-promoted electrocyclic pyran ring-opening and – ring-closing on the color of traditional cationic dye-Naphthopyran conjugates 5 and 6 and also on the fluorescence of BODIPY-Naphthopyran conjugates 7 (Scheme 2). Of significant importance to such ‘switching’ studies is a detailed understanding of the influence of the geminal (hetero)aryl substituents upon the photophysical properties of the Naphthopyrans and their photomerocyanines. We now describe our recent observations on the position of substituents on the (hetero)aryl substituents and their impact on the structure, persistence, absorbance and emission properties of the resulting photomerocyanines
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Cationic merocyanine dyes by photomodulation of [4-(Naphthopyran-3-yl)phenyl]methines
'Elsevier BV', 2013Co-Authors: Aiken Stuart, Gabbutt, Christopher D., Heron B. Mark, Clayton Danielle, Kolla, Suresh B.Abstract:A series of mono-, bis- and tris-4-(Naphthopyran-3-yl)phenyl substituted methanols were efficiently synthesised using a 4-(Naphthopyran-3-yl)phenyllithium intermediate. The resulting substituted methanols displayed good photochromism leading to the reversible generation of redeorange photomerocyanines. Acidic dehydration of the methanols gave intensely coloured cations which, upon subsequent UV irradiation, reversibly generated cationic photomerocyanines with long wavelength absorption maxima at ca. 640 nm
Preet Mohinder Singh Bedi - One of the best experts on this subject based on the ideXlab platform.
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synthesis and evaluation of naphthoflavones as a new class of non purine xanthine oxidase inhibitors
Bioorganic & Medicinal Chemistry Letters, 2014Co-Authors: Harbinder Singh, Sahil Sharma, Ritu Ojha, Kunal Nepali, Manish K. Gupta, Preet Mohinder Singh BediAbstract:In view of reported xanthine oxidase inhibitory potential of Naphthopyrans and flavones, naphthoflavones as hybrids of the two were designed, synthesized and evaluated for in vitro xanthine oxidase inhibitory activity in the present study. The results of the assay revealed that the naphthoflavones possess promising inhibitory potential against the enzyme with IC50 values ranging from 0.62 to 41.2 μM. Structure activity relationship indicated that the nature and placement of substituents on the phenyl ring at 2nd position remarkably influences the inhibitory activity. Substitution of halo and nitro groups at ortho and para position of the phenyl ring (2nd position) remarkably favored the activity. NF-4 with p-fluoro phenyl ring was the most potent inhibitor with IC50 value of 0.62 μM. Enzyme kinetics study was also performed to investigate the inhibition mechanism and it was found that the naphthoflavones displayed mixed type inhibition. The basis of significant inhibition of xanthine oxidase by NF-4 was rationalized by molecular modeling studies.
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microwave assisted synthesis of Naphthopyrans catalysed by silica supported fluoroboric acid as a new class of non purine xanthine oxidase inhibitors
Bioorganic & Medicinal Chemistry Letters, 2014Co-Authors: Sahil Sharma, Ritu Ojha, Kunal Nepali, Kirti Sharma, Dinesh Kumar, Gagandip Singh, Preet Mohinder Singh BediAbstract:Abstract A series of Naphthopyrans was synthesized employing silica supported fluoroboric acid under solvent free conditions in a microwave reactor. The catalytic influence of HBF4–SiO2 was investigated in detail to optimize the reaction conditions. The synthesised compounds were evaluated for in vitro xanthine oxidase inhibitory activity for the first time. Structure–activity relationship analyses have also been presented. Among the synthesised compounds, NP-17, NP-19, NP-20, NP-23, NP-24, NP-25 and NP-26 were the active inhibitors with an IC50 ranging from 4 to 17 μM. Compound NP-19 with a thiophenyl ring at position 1 emerged as the most potent xanthine oxidase inhibitor (IC50 = 4 μM) in comparison to allopurinol (IC50 = 11.10 μM) and febuxostat (IC50 = 0.025 μM). The basis of significant inhibition of xanthine oxidase by NP-19 was rationalized by its molecular docking at MTE binding site of xanthine oxidase.
Gabbutt, Christopher D. - One of the best experts on this subject based on the ideXlab platform.
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Photochromic bi-Naphthopyrans
'Elsevier BV', 2015Co-Authors: Aiken Stuart, Gabbutt, Christopher D., Heron B. Mark, Kolla, Suresh B.Abstract:A series of novel 3-aryl-(3,3-diaryl-3H-naphtho[2,1-b]pyran-8-yl)-3H-naphtho[2,1-b]pyrans has been accessed from 6-bromo-2-naphthol via a four step transformation. Acylation of the dianion derived from the treatment of 6-bromo-2-naphthol with n-butyllithium with Weinreb amides and subsequent reaction with a 1,1,-diarylprop-2-yn-1-ol gave 8-aroyl-3H-naphtho[2,1-b]pyrans in good yield. Addition of lithium trimethylsilylacetylide to the foregoing 8-aroylNaphthopyrans proceeded smoothly with base mediated desilyation to afford the target bi-Naphthopyrans upon acid-catalysed reaction with 2- naphthol. Preliminary evaluation of the photochromic response of the new bi-Naphthopyrans revealed reversible independent Naphthopyran ring-opening leading to a complex photochromic signature
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Cationic merocyanine dyes by photomodulation of [4-(Naphthopyran-3-yl)phenyl]methines
'Elsevier BV', 2013Co-Authors: Aiken Stuart, Gabbutt, Christopher D., Heron B. Mark, Clayton Danielle, Kolla, Suresh B.Abstract:A series of mono-, bis- and tris-4-(Naphthopyran-3-yl)phenyl substituted methanols were efficiently synthesised using a 4-(Naphthopyran-3-yl)phenyllithium intermediate. The resulting substituted methanols displayed good photochromism leading to the reversible generation of redeorange photomerocyanines. Acidic dehydration of the methanols gave intensely coloured cations which, upon subsequent UV irradiation, reversibly generated cationic photomerocyanines with long wavelength absorption maxima at ca. 640 nm
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The synthesis and properties of Naphthopyran– boradiazaindacene conjugates
Pergamon, 2012Co-Authors: Gabbutt, Christopher D., Heron B. Mark, Kilner Colin, Kolla, Suresh B.Abstract:Three new 3,3-diaryl-3H-naphtho[2,1-b]pyran–boradiazaindacene conjugates have been synthesised. The Naphthopyran–boradiazaindacene conjugates exhibit a weaker photochromic response relative to the simple Naphthopyrans with the photomerocyanines fading relatively quickly. Photochromic switching of the Naphthopyran unit results in a decrease in the fluorescence intensity for only the most persistent photomerocyanine. A crystal structure shows that the units are essentially orthogonally disposed and that the boradiazaindacene core is extensively delocalised
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The synthesis and properties of vinyl substituted Naphthopyrans and their styrene copolymers
'Elsevier BV', 2012Co-Authors: Blackwell, Catherine J., Gabbutt, Christopher D., Guthrie, James T., Heron B. MarkAbstract:A comprehensive series of mono-, di- and tri-bromo-3H-naphtho[2,1-b]pyrans was synthesised by the traditional union of a 2-naphthol with an alkynol. The bromine atom(s) in these Naphthopyrans was readily replaced by a vinyl group using a Suzuki coupling reaction with vinyl boronic anhydride pyridine complex. The efficiency of the Suzuki vinylation reaction decreases with the increasing number of bromine atoms to be substituted. The vinylNaphthopyrans served as styrene analogues and readily underwent a thermally initiated free radical addition co-polymerisation with styrene to efficiently afford low molecular weight poly(styrene-co-Naphthopyrans). The photochromic response of the bromoNaphthopyrans and vinylNaphthopyrans followed the established colour-structure relationships for photochromic Naphthopyrans. The photochromic response of toluene solutions of the poly(styrene-co-Naphthopyrans) was characterised by a hypsochromic shift of the λmax relative to that recorded for the vinylNaphthopyran monomers. Increased half-lives were noted for the copolymers derived from the bis- and tris-vinylNaphthopyrans where some degree of crosslinking was expected. A further hypsochromic shift in λmax resulted for the thin films of the poly(styrene-co-Naphthopyrans). Of particular note was the behaviour of the 3-(2-vinylphenyl)-3-phenylNaphthopyran which gave the typical yellow colour of the photomerocyanine coupled with the predictable large half-life. However, all photochromism of this Naphthopyran was lost upon polymerisation suggesting that an alternative pathway supervenes in the expected polymerisation sequence
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The intramolecular capture of thermally generated merocyanine dyes derived from Naphthopyrans: Photochromism of 5-(diarylhydroxymethyl)-2H-naphtho[1,2-b]pyrans
Pergamon, 2012Co-Authors: Gabbutt, Christopher D., Heron B. Mark, Gibbons Lucy, Kolla, Suresh B.Abstract:A series of 2H-naphtho[1,2-b]pyrans bearing a diarylmethanol unit at C-5 have been synthesised by the addition of an excess of an aryllithium reagent to alkyl 2H-naphtho[1,2-b]pyran-5-carboxylate precursors. These Naphthopyrans show photochromism when exposed to ultraviolet irradiation and also generate intense colours at low pH through triarylmethine cation generation. However, photochromism of the triarylmethine cation derived from the Naphthopyran unit could not be detected. An irreversible cascade process initiated by the thermally-induced ring-opening of the diarylmethanol substituted 2H-naphtho[1,2-b]pyrans in the presence of an acid catalyst afforded novel benzopentalenonaphthalenone dyes
Michel Frigoli - One of the best experts on this subject based on the ideXlab platform.
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A helical Naphthopyran dopant for photoresponsive cholesteric liquid crystals
Chemical Communications, 2017Co-Authors: Yuna Kim, Michel Frigoli, Nicolas Vanthuyne, Nobuyuki TamaokiAbstract:The first photoresponsive cholesteric liquid crystal comprising a photoisomerizable helical Naphthopyran derivative dopant and a nematic liquid crystal is reported. An unprecedented helical twisting power switching ratio of over 90% allowed us to demonstrate multi-cycle rotational motion of micro-objects by UV light irradiation.
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The control of photochromism of [3H]-Naphthopyran derivatives with intramolecular CH-? bonds
Organic Letters, 2012Co-Authors: Michel Frigoli, Stephanie Delbaere, Francois Maurel, Jérôme Marrot, Jerome Berthet, Maria M. OliveiraAbstract:The photochromism of [3H]-Naphthopyran derivatives can be switched from T-type to inverse- or P-type through the manipulation of relative thermodynamic stabilities of open isomers with intramolecular CH-? bonds.
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Bridging the visible: The modulation of the absorption by more than 450 nm
Organic Letters, 2010Co-Authors: Stephanie Delbaere, G. Vermeersch, Michel Frigoli, Georg H MehlAbstract:The coexistence of 18 isomers, identified by NMR spectroscopy and gathered into six states with very different absorption properties, is observed upon irradiation with selective wavelengths of a triphotochromic system joining two Naphthopyran entities through a dithienylethene bridge. The sequential electronic coupling of photochromic groups resulted in an absorption behavior reaching far into NIR.
