Multitarget synthetic strategies to access novel photochromic 3H-naphtho2,1-bpyrans decorated with pyridyl units are described. The new pyridyl-substituted 3H-naphtho2,1-bpyrans display good ...photochromic properties with reversible generation of photomerocyanines, which exhibit mainly orange/red hues. Photochromic parameters including photocolorability and persistence of color vary tremendously on structural modification of the naphthopyran core.
Intrinsically thermochromic fluorans Azizian, Farid; Field, Amanda J; Heron, B Mark ...
Chemical communications (Cambridge, England),
2012-Jan-18, Letnik:
48, Številka:
5
Journal Article
Recenzirano
A Suzuki coupling strategy has been employed to access a series of novel fluorans substituted with a phenolic moiety. These fluorans display good thermochromism in methyl stearate and obviate the ...need for traditional complex formulations containing acidic colour developers.
The last few years have seen an explosion of interest in traditional photochromic systems not only for their applications in variable transmission devices, which continues to attract commercial ...interest, but also for the ability of these molecules to undergo structural and electronic reorganisation which has been seized upon by materials scientists for the development of switches, logic gates, photoinduced molecular motions such as rotors and fibrils, and photoregulation of drug availability. This comprehensive review examines, for the first time, the ‘dark side of photochromism’; negatively photochromic systems which are coloured in their ground state and reversibly photobleach upon exposure to electromagnetic radiation with a wavelength over ca. 400 nm i.e. visible light responsive systems. This review is organised by structural class and examines their synthesis, structure, key spectroscopic data for coloured and bleached species, structure – switching relationships and applications. The usefulness of these negatively photochromic systems is only gradually coming to the fore with the advantages of low energy activation c.f. conventional Uv-activated switches, enabling the modulation of a plethora of useful optical and physical properties and the design of new materials with broad ranging applications.
•The phenomenon of negative photochromism of organic compounds is reviewed.•T-Type negative photochromic systems are discussed.•P-Type negative Photochromic systems are discussed.•Spectroscopic data for negative photochromic organic compounds is presented.•Applications of negative photochromic organic compounds have been identified.
Heating 4-methoxy-1-naphthol with a 1,1-diarylprop-2-yn-1-ol gave the 2,2-diaryl-6-methoxy-2H-naphtho1,2-bpyran together with the novel merocyanine, ...(E)-2-3',3'-bis(aryl)allylidene-4-methoxynaphthalen-1(2H)-one. Brief UV-irradiation of the pyran favoured the formation of the (Z)-merocyanine with longer irradiation and/or acidic conditions favouring the (E)-isomer.
Diversely substituted 1,2-oxathiine 2,2-dioxides, including 3,5,6-triaryl-, 3,6-diaryl-, 3,5-diaryl-, 5,6-diaryl- and selected fused heterocyclic analogues, have been efficiently obtained by the ...application of a mild Cope elimination of a 4-amino moiety from the requisite 4-amino-3,4-dihydro-1,2-oxathiine 2,2-dioxides, which themselves were readily obtained by the addition of sulfenes to enaminoketones.
The addition of sulfenes to substituted enaminoketones, followed by a facile Cope elimination, provides efficient access to a diverse series of 1,2-oxathiine 2,2-dioxides.
The core promoter plays a central role in setting metazoan gene expression levels, but how exactly it “computes” expression remains poorly understood. To dissect its function, we carried out a ...comprehensive structure–function analysis in Drosophila. First, we performed a genome‐wide bioinformatic analysis, providing an improved picture of the sequence motifs architecture. We then measured synthetic promoters’ activities of ~3,000 mutational variants with and without an external stimulus (hormonal activation), at large scale and with high accuracy using robotics and a dual luciferase reporter assay. We observed a strong impact on activity of the different types of mutations, including knockout of individual sequence motifs and motif combinations, variations of motif strength, nucleosome positioning, and flanking sequences. A linear combination of the individual motif features largely accounts for the combinatorial effects on core promoter activity. These findings shed new light on the quantitative assessment of gene expression in metazoans.
Synopsis
A large‐scale structure‐function analysis of ~3,000 synthetic promoters reveals the sequence determinants of Drosophila core promoters.
Mutational analysis using synthetic promoters reveals a strong impact of various types of mutations on the promoter activity.
The linear combination of the individual motif features largely accounts for the combinatorial effects on core promoter activity.
The analysis of the response to an external stimulus (hormone activation) shows a correlation between the hormone responsiveness and the core promoter architecture.
A large‐scale structure‐function analysis of ~3,000 synthetic promoters reveals the sequence determinants of Drosophila core promoters.
In this work, the vibrational spectral analysis was carried out using FT-IR and FT-Raman spectroscopy of 3,4-dichlorobenzophenone. The computations were performed at DFT theory using 6-311+G∗∗ basis ...set to get optimized geometry and vibrational wave numbers of the normal modes of the title compound. Comparison of simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. Display omitted
•FT-IR, FT-Raman and UV–Vis investigations of 3,4-DclBP were carried out.•Molecular structure was studied using B3LYP/6-311+G∗∗ method.•The PED calculation provides a strong support for the frequency assignment.•NBO analysis used to explain the interaction between electron donors and acceptors.
The vibrational frequencies of 3,4-dichlorobenzophenone (DCLBP) were obtained from the FT-IR and Raman spectral data, and evaluated based on the Density Functional Theory using the standard method B3LYP with 6-311+G(d,p) as the basis set. On the basis of potential energy distribution together with the normal-co-ordinate analysis and following the scaled quantum mechanical force methodology, the assignments for the various frequencies were described. The values of the electric dipole moment (μ) and the first-order hyperpolarizability (β) of the molecule were computed. The UV-absorption spectrum was also recorded to study the electronic transitions. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The NBO analysis, to study the intramolecular hyperconjugative interactions, was carried out. Mulliken’s net charges were evaluated. The MEP and thermodynamic properties were also calculated. The electron density-based local reactivity descriptor, such as Fukui functions, was calculated to explain the chemical selectivity or reactivity site in 3,4-dichlorobenzophenone.
A series of spironaphthopyrans has been synthesised by the acid-catalysed condensation between either a substituted 1-naphthol or 2-naphthol and the propargylic alcohol derived from the addition of ...lithium trimethylsilylacetylide to a 7H-benzocycloheptan-7-one with subsequent in situ silyl group removal. The photochromism of the novel spironaphthopyrans was characterised by a bathochromically shifted λmax coupled with a relatively quick initial fade of the photogenerated species relative to the comparable diphenyl substituted model compounds. After initial fading a relatively intense residual colour persisted for the spironaphthopyrans.
Neuromorphic engineering promises to have a revolutionary impact in our societies. A strategy to develop artificial neurons (ANs) is to use oscillatory and excitable chemical systems. Herein, we use ...UV and visible radiation as both excitatory and inhibitory signals for the communication among oscillatory reactions, such as the Belousov–Zhabotinsky and the chemiluminescent Orban transformations, and photo‐excitable photochromic and fluorescent species. We present the experimental results and the simulations regarding pairs of ANs communicating by either one or two optical signals, and triads of ANs arranged in both feed‐forward and recurrent networks. We find that the ANs, powered chemically and/or by the energy of electromagnetic radiation, can give rise to the emergent properties of in‐phase, out‐of‐phase, anti‐phase synchronizations and phase‐locking, dynamically mimicking the communication among real neurons.
Some light conversation: UV/visible radiation is a rich code for communicating excitatory and inhibitory signals among oscillatory reactions and photo‐excitable systems, functioning as artificial neuron models. Pairs or triads of such chemical systems organized in both feed‐forward and recurrent networks synchronize in phase, out of phase, in anti‐phase and phase‐locking as real neurons do through chemical neuro‐transmitters.
Neuromodulation is the alteration of neuronal and synaptic properties in the context of neuronal circuits. It allows anatomically defined circuits to produce multiple outputs reconfiguring networks ...into different functional circuits. In this work, neuromodulation is mimicked using a solution of two direct photochromic compounds, a naphthopyran and a spirooxazine, which are models of phasic excitable neurons, sensitive to UV radiation. When the system, constituted by the two photochromic compounds, receives a UV signal, it behaves as a recurrent network with mutual inhibitory actions. The network responds to different UV wavelengths by changing its photo-excitability, synaptic strength, wiring of the circuit, and dynamics. These results contribute to the development of neuromorphic engineering. They will promote the design of artificial neural networks with a larger number of nodes, communicating through optical signals. These networks will be the essential ingredients of the new-generation brain-like computing machines complementing current electronic computers.
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