Biomimetic nanoplatforms constructed from dialkylaminostyryl hetarene dyes and phospholipids exhibiting selective fluorescent response to specific proteins.

The present work explores the specificity of supramolecular assemblies comprising dialkylaminostyrylhetarene dye molecules incorporated into phosphatidylcholine (PC) or phosphatidylserine (PS) aggregates. In PS-based assemblies, the dyes demonstrate a concentration-dependent fluorescent response, distinguishing anionic proteins such as bovine serum albumin (BSA) and pepsin from lysozyme (LYZ) in aqueous solutions. Conversely, no significant response is observed when the dyes are incorporated into the well-organized bilayers of neutral PC. The fluorescent response arises from the binding of dyes to proteins, leading to the detachment of dye molecules from the assemblies, rather than from the binding of proteins to the assemblies, although the latter process is facilitated by electrostatic attraction. Thus, both the poor ordering of PS molecules and the interfacial arrangement of the dyes are prerequisites for the fluorescent response of dye-PS aggregates. The structure of the dyes significantly impacts the spectral features of dye-PS and dye-protein assemblies. An optimal dye structure has been identified for the recognition of BSA, with a limit of detection (LOD) of 10.8 nM.

Synthesis of D-π-A'-π-A Chromophores with Quinoxaline Core as Auxiliary Acceptor and Effect of Various Silicon-Substituted Donor Moieties on Thermal and Nonlinear Optical Properties at Molecular and Material Level.

Novel D-π-A'-π-A chromophores with quinoxaline cores as auxiliary acceptors and various donor moieties (aniline, carbazole, phenothiazine, tetrahydroquinoline) containing bulky tert-butyldimethylsilyloxy (TBDMSO) groups and tricyanofuranyl (TCF) acceptors with bulky cyclohexylphenyl substituents were synthesized via eight- to nine-step procedures, and their photo-physical and thermal properties were investigated. The values of the chromophores' first hyperpolarizabilities were calculated in the framework of DFT at the M06-2X/aug-cc-pVDZ computational level; the effect of the introduction of the TBDMSO group into the donor fragment is shown to be inessential, as this group is not coupled to the π-conjugated system of the chromophore. The chromophore with the tetrahydroquinoline donor has a first hyperpolarizability value of 937 × 10-30 esu, which is the highest for the studied chromophores. Atomistic modeling of composite materials with the studied chromophores as guests demonstrated that the presence of bulky substituent in the donor fragment prevents notable aggregation of chromophores, even at high chromophore content (40 wt.%). The nonlinear optical performance of guest-host materials with 25 and 40 wt.% of suggested chromophore content was studied using a second harmonic generation technique to give the NLO coefficient, d33 up to 52 pm/V.

Composing NLO Chromophore as a Puzzle: Electrochemistry-based Approach to Design and Effectiveness.

A series of D-π-A, D-π-D'-π-A, D-π-A'-π-A nonlinear optical chromophores with vinylene π-electron bridges or bridges with π-deficient/π-excessive heterocyclic moieties along with the corresponding precursors D-vinylene, D-π-D', D'-π-A, D-π-A' and A'-π-A are synthesized and studied both experimentally and computationally. The effect of the heterocycle in the π-electron bridge on the oxidation/reduction potentials and the energy gap (ΔEel ) is investigated in detail. The properties of the D-π-A'(D')-π-A chromophores are shown to correlate with those of building blocks: the oxidation potential is determined by the D-vinylene, and the reduction potential is determined by A'(D')-π-A truncated compounds. The contribution of the acceptor to the oxidation potential of chromophores in comparison with those of the precursors was estimated and analyzed in terms of electronic communication between the end groups. A good correlation between the ΔEel and the chromophores' first hyperpolarizability is revealed.

Characterization of Conjugation Effects in the Series of Quinoxaline-2-ones by Means of Vibrational Raman Spectroscopy.

A broad series of quinoxalinone-based π-conjugated donor-acceptor fluoro- and NLO-phores is characterized by means of Raman spectroscopy and single-crystal X-ray analysis supported by quantum chemical computations. Intense Raman spectroscopic markers that allow the differentiation of even closely related structures are identified. The intensities of these bands are shown to be related to the conjugation of the different molecular moieties, and they can provide an estimation of its extent. The intensity redistribution between these markers serves as a source of auxiliary structural information capable of pointing to a distortion of the conjugation or to the influence of aggregation effects in the condensed state. A simple relation between the intensity of the marker and the position and oscillator strength of the lowest-energy electronic absorption band of quinoxalinones allows a linking of the Raman effect with the optical properties of these compounds, which can be used for the rational design of novel species with improved optical characteristics.

Antimicrobial activity of imidazo[1,5-a]quinoxaline derivatives with pyridinium moiety.

3-Phenyl(methyl)-5-alkyl-1-(pyridin-3-yl)imidazo[1,5-a]quinoxalin-4-ones (2a-f) and their N-alkyl-pyridinium salts (3a-o), including 1,n-bis{3-(3-phenylimidazo[1,5-a]quinoxalin-4(5H)-on-1-yl)pyridinium}alkane dibromides (4a-d, 5, 6) have been synthesized. It has been established that the antimicrobial properties of imidazo[1,5-a]quinoxaline derivatives are connected with the presence of various alkyl substituents in the position 1 of the pyridine ring and in the position 5 of the imidazo[1,5-a]quinoxaline system. Chlorides and iodides are more active towards bacteria than fungi. Compounds 3d, 3e, 3m and 3n showed an effective bacteriostatic activity. Compound showed not only well defined bacteriostatic activities but also good fungistatic activities, with the MIC values comparable with the reference drugs. Toxicity of more effective (imidazo[1,5-a]quinoxalin-4-on-1-yl)-1-pyridinium halides was examined in mice.

seco-C/D ring analogues of ergot alkaloids. Synthesis via intramolecular Heck and ring-closing metathesis reactions.

[reaction: see text] Intramolecular Heck and ring-closing metathesis reactions on key intermediates 10 and 15, respectively, provide efficient entries into seco-C/D ring analogues of Ergot alkaloids 12 and 16, compounds of potential synthetic and biological interest.

Synthesis of constrained raloxifene analogues by complementary use of Friedel-Crafts and directed remote metalation reactions.

New constrained heterocyclic analogues, 2a,b and 3, of Raloxifene (1) have been prepared by complementary Directed remote Metalation (DreM)/Friedel-Crafts cyclization approaches. Utilization of a benzylidene-thiolactone rearrangement was successfully implemented to construct benzothiophenes 13a-c in good yields. Selective deprotection of 13a and 13b induced by complexation followed by triflation gave 18 and 23, thereby allowing efficient Suzuki-Miyaura cross coupling with borolane 16 to give biaryls 19 and 24. Treatment of 19 with BCl(3) induced an intramolecular para Fridel-Crafts cyclization and concomitant double deprotection to furnish analogue 2a, a new 5,6,6,6-(C(4)S-C(6)-C(6)-C(6)) sulfur-containing heterocycle. Exposure of 25 with excess LDA induced a DreM cyclization delivering the ortho-substituted 5,6,6,6-(C(4)S-C(6)-C(6)-C(6)) heterocylic analogue 26 in 70% yield. Similar treatment of 13c and 27 afforded 30, representing the novel 5,5,6,6-(C(4)S-C(5)-C(6)-C(6)) ring system, which was subjected to Suzuki-Miyaura cross coupling with 16 to give the biaryl 31 in 93% yield; deprotection furnished the final constrained analogue 3.

Directed Metalation Linked to Transition Metal Catalyzed Cascade Reactions: Two Total Syntheses of Plicadin, the Alleged Coumestan from Psoralea plicata.

The oxygen-rich heterocyclic compound 1-which was proposed to be the structure of plicadin, the alleged naturally occurring coumestan from the herb Psoralea plicata-was synthesized by the rational combinations of directed ortho and remote metalation reactions with cascades of Negishi, Sonogashira, Castro-Stephens, and carbamoyl Baker-Venkataraman reactions.