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The molecular engineering of chromophores that enables the controlled and reliable formation of hierarchical solid-state architectures is at the forefront of developing hybrid semiconducting materi...

Two regioisomeric pairs of heptahelical mono- and biscoumarins that are differentiated by "inward" and "outward" disposition of the pyran-2-one moiety have been synthesized and investigated to understand the influence of helicity on excited-state and chiroptical properties. A slight variation in the helicities is found to manifest in contrasting excited-state properties of coumarin-annelated heptahelicenes; in addition to the intramolecular charge transfer, structural relaxation in the excited state is shown from theoretical calculations to cause decrease in the fluorescence quantum yield for a system with higher helicity. The optically pure enantiomers of heptahelical coumarins exhibit helicity-dependent chiroptical properties, namely, specific rotations, molar ellipticities, Cotton effects, and anisotropic dissymmetry factors. Theoretical calculations point to factors that are not readily explicable.

We show that n-doping supramolecular assemblies built from perylene diimide units provides a means to modulate the structure-function properties of these materials. In addition to highlighting the design principles, a combination of spectroscopic and microscopic characterization correlates an increase in the free-exciton bandwidth with the formation of mesoscale hierarchical superstructures.

A zinc metal–organic framework, i.e., Zn-MOF (Zn-DBC), with ca. 27% solvent-accessible void volume was synthesized from a rationally designed tetraacid based on sterically insulated dibenzo[g,p]chr...

MediaChromes are molecular systems characterized by a rigid aromatic backbone bearing electron-donating (D) and accepting (A) groups conjugated in the so-called push-pull D–π–A fashion. Electronic excitation of such systems results in increase of the dipole moment in the excited state due to intramolecular charge transfer (ICT), leading to remarkable excited-state properties. We have investigated fluorosolvatochromic and halochromic (acidochromic) behavior of carbazolo-phenazine (CP), a new bipolar molecular system characterized by conjoined donor carbazole and acceptor phenazine heterocycles. CP is shown to exhibit exceptional fluoromediachromic behavior due to ICT in the excited state; the difference in the dipole moments of ground- and singlet-excited states of CP is ca. 3.6 D units. ICT occurs also in the ground state upon protonation, which manifests in brilliant naked-eye visible violet coloration, namely, acidochromism.

Access to novel bipolar carbazolo-phenazines is demonstrated by one-pot IBX-initiated multistep cascade, which involves oxidation of 2-naphthols to 1,2-naphthoquinones, Diels-Alder cycloaddition, aerial dehydroaromatization and cyclocondensation. With unprotected dienic indolylacrylates, N H⋯O hydrogen bonding in the transition state controls the product selectivity almost exclusively in favor of Diels-Alder cycloaddition over the competing Michael addition. The utility of one of the carbazolo-phenzines as applied to selective naked-eye sensing of fluoride is demonstrated.

Locking-in the conformation of supramolecular assemblies provides a new avenue to regulate the (opto)electronic properties of robust nanoscale objects. In the present contribution, we show that the covalent tethering of a perylene bisimide (PBI)-derived supramolecular polymer with a molecular locker enables the formation of a locked superstructure equipped with emergent structure-function relationships. Experiments that exploit variable-temperature ground-state electronic absorption spectroscopy unambiguously demonstrate that the excitonic coupling between nearest neighboring units in the tethered superstructure is preserved at a temperature (371 K) where the pristine, non-covalent assembly exists exclusively in a molecularly dissolved state. A close examination of the solid-state morphologies reveals that the locked superstructure engenders the formation of hierarchical 1D materials which are not achievable by unlocked assemblies. To complement these structural attributes, we further demonstrate that covalently tethering a supramolecular polymer built from PBI subunits enables the emergence of electronic properties not evidenced in non-covalent assemblies. Using cyclic voltammetry experiments, the elucidation of the potentiometric properties of the locked superstructure reveals a 100-mV stabilization of the conduction band energy when compared to that recorded for the non-covalent assembly.

Diarylbenzo- and naphthopyrans are one of the important and well-known classses of organic photochromic systems. Their photolysis leads to highly colored o -quinonoid intermediates. The mechanistic details and spectrokinectic properties of the photogenerated colored intermediates have been extensively studied. Accordingly, stereoelectronic effects have been shown to play a crucial role in controlling properties such as spectrokinetics, fatigue resistance and colorability. Much research continues unabated to develop photochromic materials with properties that surpass the existing ones for application in ophthalmic lenses as well as optical data storage devices. In the realm of materials chemistry, the diarylpyran unit is presently exploited as an essential design element to produce functional materials. Given the facile synthetic access to molecular systems that respond to light as an external stimulus leading to widely distinct physicochemical properties, we believe that more exciting research based on diarylpyran photochemistry will germinate in materials chemistry and biology in the near future. This review with a coverage of the phenomenon since its inception to the present state of application for functional materials–through synthesis and mechanistic details–should serve as an invaluable resource to an uninhibited chemist to exploit the photochromism of diarylpyrans for diverse functions/applications.

Biginelli reaction involves acid-catalyzed one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs) using easily-accessible starting materials, namely, aldehyde, active methylene compound and (thio)urea. DHPMs have stimulated resurgence of interest in the past two decades due to their wide ranging pharmacological activities and presence of diverse natural products. Presently, green approaches to asymmetric Biginelli reaction are being explored for bioactive chiral DHPMs. In materials chemistry, DHPMs are increasingly finding applications in the development of materials such as polymers, adhesives, fabric dyes, etc. In view of the ease with which the Biginelli reaction is conducted, many exciting prospects await for its exploitation in various fields.

2D metal-organic nanosheets (MONs), akin to graphene, have aroused immense contemporary interest. In our quest to develop functional 2D MONs based on organic linkers designed de novo, we reasoned that benzene-tetrabenzoic acid, which has been exploited tremendously in the construction of pillared metal-organic frameworks (MOFs), could be maneuvered readily to access redox-active MONs based on the benzoquinone/hydroquinone redox couple. Herein, we show that the self-assembly of 2,3,5,6-tetrakis(p-carboxyphenyl)hydroquinone H4 BTA with Zn(NO3 )2 does lead to 2D metal-organic nanosheets that stack down the y axis, affording a layered Zn MOF. Although the crystals of the latter do not exhibit a discernible chemically induced redox switching behavior, the 2D MONs accessed by ultrasound-induced liquid-phase exfoliation (UILPE) lend themselves to a facile redox switching behavior. Treatment of a dispersion of the 2D MONs in methanol with phenyliodine(III) diacetate (PIDA) results in the oxidation of the hydroquinone core to benzoquinone. Remarkably, the latter can be reverted to the former by treatment with ascorbic acid as a reducing agent; indeed, the redox process can be made out by the naked eye. The results constitute the first example of chemically induced redox switching of 2D MONs. In view of emergent applications of 2D materials in general and MONs in particular, for example, improvement of the performance of membranes in separations by doping with MONs, the redox-switchable property may lead to the development of unique materials with heretofore unexplored potential.

Diarylbenzopyrans and their annulated derivatives are a class of photochromic compounds, which have been extensively investigated for photochromism. In fact, some naphthopyrans are employed industrially in ophthalmic lens applications. Photoirradiation of 2,2-diphenylbenzopyran leads to the formation of colored o-quinonoid intermediates. The latter revert too rapidly to allow their observation only at low temperatures (173–263 K). Annulation and other strategies are exploited to observe the colored o-quinonoid intermediates that persist for a few minutes at room temperature. We have examined photochromism of a set of silyloxy-substituted 2,2-diphenylbenzo- and naphthopyrans to explore how the mesomeric effects transmitted by the strongly e-donating silyloxy group substituted in the ring and at phenyl groups manifest in the spectrokinetic properties of their photogenerated colored o-quinonoid intermediates. We show that silyloxy substitution in the benzopyran ring leads to remarkable stabilization of the colored intermediates to enable their persistence at 283 K for a few minutes. In contrast, similar substitution in the C2-phenyl rings destabilizes the colored intermediates.

Phenyl/arylethynylation of 2,2-diphenylbenzopyrans (i.e., chromenes) permits modulation of the spectral properties of photogenerated colored o-quinonoid intermediates, and brings about remarkable stabilization of the latter, rendering the phenomenon of photochromism observable readily at room temperature. Modification of the spectrokinetic properties of the o-quinonoid intermediates are a consequence of resonance effects, with the substituent effects being relayed nicely from one end of the molecule to the other. Functionalization at the 6-position of the chromene nucleus leads to more redshifted absorptions as well as to increased lifetimes of the colored species when compared with functionalization at the 7-position. Given that photochromism is observable in the parent chromene at only low temperatures, phenyl/arylethynylation, which precludes steric inhibition of resonance, is demonstrated to render bleaching kinetics of the colored intermediates that approach those reported for industrially relevant diarylnaphthopyrans.

Anionic merocyanine colored dyes based on (4-nitro/cyanophenyl)-substituted thiazol-2-hydrazides (THAs), which are donor-π-acceptor type push-pull molecular systems and characterized with a strong intramolecular charge transfer (ICT) in the ground state, have been examined as reverse solvatochromic systems. THAs are shown to exhibit both positive and negative solvatochromism with a reversal of the latter occurring for solvents of ET(30) value of ca. 45. The observed behavior is traceable to relative contributions of benzenoid and quinonoid resonance forms of the THAs and their stabilization by solvents to different degrees. Solvatochromic studies in binary mixtures of polar aprotic and protic solvents reveal that the latter are always preferred in the solvation microsphere of THAs. Multiparametric treatment of the ET(dye) parameters by Catalan and Kamlet-Taft linear solvation energy relationships (LSERs) compellingly bears out the remarkable influence of hydrogen-bond donating (HBD) acidity, dipolarity and polarizability of the media on the spectral properties of the anionic dyes; hydrogen-bond accepting (HBA) basicity of the solvents is found to influence the least.

The fluoride-mediated desilylation reaction has been exploited, for the first time, to trigger ring-opening of photochromic diarylbenzo-/naphthopyrans into highly colored anionic merocyanine dyes with high molar absorptivities to permit naked-eye sensing. The absorption spectral shifts, i.e., differences in the absorption maxima of colorless and colored forms, observed for a rationally designed set of silyloxy-substituted diarylpyrans subsequent to fluoride-induced ring opening are remarkably high (330–480 nm), and are unknown for any colorimetric probe. In particular, the disilyloxy-substituted diphenylnaphthopyran and its analog, in which the diphenyl groups are fused in the form of fluorene, allows “naked-eye” detection of fluoride in subppm levels (

Oseltamivir phosphate is licensed for the treatment of patients with influenza virus infection. Two LCMS/MS methods for simultaneous quantification of Oseltamivir and its active metabolite, oseltamivir carboxylate in human plasma were described here. After solid phase extraction sample was separated either on a reversed phase C18 column with a stepwise gradient using 0.05% formic acid and methanol or a cation-exchange column using an isocratic mobile phase (7 mM Ammonium formate, pH 3.5 ± 0.2: Methanol: 50:50, v/v). Flow rate of 1 mL/min was maintained in both cases. A triple quadrupole mass spectrometer operating in the positive ionization mode was used for detection and drug quantification. Both methods were validated over a range of 0.52ng/ml to 207.00 ng/ml for Oseltamivir and 4.08 ng/ml to 1200.00 ng/ml for Oseltamivir Carboxylate. Deuterated Oseltamivir and Oseltamivir carboxylate were used as internal standards. The accuracies and precisions for Oseltamivir were between 91–102% and 0.9 – 13.7% for all concentration levels. The accuracies and precisions for Oseltamivir carboxylate were between 88–109% and 0.5 – 8.2% at all levels. Furthermore, Oseltamivir and its metabolite were stable in plasma ex vivo for at least 191 days when stored at −20°C or below.