Unconventional luminescence caused by hindered intra- and intermolecular mobility of molecules is of great research interest in science and technology. However, the lack of data on the effect of the structure of such compounds on the process of aggregation-induced emission and the underdevelopment of existing synthetic approaches make these studies difficult. We have developed new non-classical luminophores based on amidophosphonate and amidophosphate containing polysilsesquioxanes obtained by a simple two-stage synthetic route: monomers were obtained by nucleophilic substitution reactions at the P(V) atom, and the corresponding polymers were obtained by hydrolytic polymerization. Luminescent properties of both monomers and polymers were described, and it was shown that luminescence by cluster aggregation is also characteristic of low-molecular luminophores.

An efficient approach for an accurate quantum mechanical (QM) modeling of Raman spectra of condensed-phase systems is described. Energetically low-lying cluster structures of a molecule surrounded by an explicit shell of solvating molecules are efficiently generated at the semi-empirical tight-binding QM level and then re-optimized at the Density Functional Theory (DFT) level of theory. Such cluster models of a solvated molecule are shown to be sufficient to reproduce experimental vibrational frequencies and relative Raman intensities of several hydrogen-bonded liquids and aqueous solutions with the use of B3LYP-D3/def2-TZVP, ωB97X-3c, or B97-3c DFT methods in harmonic simulations, provided that the first solvation shell is included in the model. Analogous simulations at the computationally less demanding PBE-D3/def2-TZVP level provided less good, but still reasonably accurate, results. With the examples of acetone, acetonitrile, benzene, and their deuterated analogs, and the ionic liquid 1,3-dimethylimidazolium tetrafluoroborate, it is demonstrated that Raman spectra of liquids, where pronounced hydrogen bonds are absent, can be obtained in the gas-phase approximation. A comparison of absolute Raman intensities measured for gaseous and liquid acetone, acetonitrile, and benzene with our cluster simulations suggests that the inclusion of more than the first solvation shell is needed to reproduce the observed increase in Raman scattering cross sections in liquids relative to gases.

We demonstrate that an efficient computational protocol for accurate quantum mechanical (QM) modeling of IR and Raman spectra of condensed-phase systems is applicable to aqueous zwitterions of L-alanine and L-valine. The approach is based on generating energetically low-lying cluster structures consisting of the solute surrounded by an explicit solvation shell, optimized at the DFT level. Such cluster models are shown to reliably reproduce experimental vibrational frequencies and relative IR and Raman intensities of both amino acids at the B3LYP-D3/def2-TZVP level, provided that 25 water molecules are included. The accuracy of the simulations is sufficient to resolve all three conformers of valine and to identify their spectroscopic signatures. Relative conformer populations are estimated from the experimental intensities of the corresponding conformational marker bands, and conformationally averaged optical rotations (OR) of valine are computed using several QM protocols for [α]D. A comparative analysis of the full set of computed OR values for both amino acids yields an intrinsic margin of error in TDDFT calculations of [α]D of approximately 50° cm3/(g dm).

A series of vicinal bis(diphenylphosphine oxide)ethanes were synthesized via the α,β-bisphosphorylation of aryl-substituted acetylenes. Optimized reaction conditions were established, affording the desired compounds in moderate to good yields. The synthesized derivatives were evaluated for cytotoxic activity against a panel of cancer cell lines (M-HeLa, MCF-7, HuTu 80, A549), and nonmalignant cells (WI-38 and Chang Liver). The highest efficacy was observed against the M-HeLa cell line, with IC50 values ranging from 1.4 to 3.9 μM, which is 9-25 times more potent than the activity of sorafenib, a reference drug. Lead compounds 3g and 3d demonstrated selectivity toward M-HeLa cells compared to Chang liver cells, suggesting their potential therapeutic value. Mechanistic investigations revealed that 3g and 3d induce dose-dependent apoptosis via the mitochondrial pathway. Key findings indicate G2/M phase cell cycle arrest independent of the p53 pathway. Furthermore, a significant decrease in tubulin polymerization-promoting protein (TPPP) levels was observed, indicating tubulin depolymerization and antimitotic activity. Additionally, compound 3d exhibited inhibitory activity against cyclin-dependent kinase 2 (CDK2). These results position bis(diphenylphosphine oxide) derivatives as a promising scaffold for the development of novel anticancer agents.

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.

Combined UV-vis and quantum chemical studies of the structural flexibility and tautomerism of 6-R-3-hydroxy-2-pyrazine carboxamides in solutions revealed that their keto-enol transformations are accompanied by the deprotonation of enol tautomers and the formation of the corresponding anionic species. Both the solvent and the 6-R substituent strongly influence the relative abundance of the above forms in solutions. Anions are not formed in 1,2-dichloroethane (DCE), but the probability of deprotonation in neutral water and N,N-dimethylformamide (DMF) increases in the order R = H < F < NO2. Only enol tautomers of all solutes are found in DCE. DMF stabilizes keto forms only moderately and assists much strongly in the deprotonation of all three compounds. Water tends to stabilize both keto tautomers and deprotonated anions: the keto form dominates in the case of R = H (antiviral drug T-1105), the anions are found exclusively for R = NO2, and the aqueous solution of another antiviral drug, favipiravir (R = F), contains both the keto tautomer and the anionic form. The results of quantum chemical free energy calculations are in agreement with the experimental observations.

As in the case of cytosine [Phys. Chem. Chem. Phys. 2023, 25, 24121-24128], Raman and infrared (IR) spectra of aqueous thymine and its N-deuterated derivative, thymine-d2 have been computationally reproduced and interpreted with the use of the recently developed efficient protocol to explicit quantum mechanical modeling of structure and IR spectra of liquids and solutions [J. Phys. Chem. B, 2020, 124, 6664-6670]. A cluster model of a solute surrounded by 30 water molecules is shown to be sufficient to reproduce experimental vibrational frequencies and relative Raman intensities with the use of B3LYP-D3/def2-TZVP or B3LYP-D3/aug-cc-pVDZ simulations. Analogous PBE-D3 computations provided a less good, but still reasonably accurate, modeling of Raman spectra. It is shown that strong changes of frequencies and relative intensities of the Raman bands of thymine, caused by its hydration, can be interpreted mainly as a result of hydrogen bonding with 6 nearest water molecules. Non-negligible improvement of the quality of simulations for larger clusters comprising water molecules that do not have direct contacts with the solute, suggests that spectroscopic effects of hydration should be ascribed to the joined action of solute-solvent and solvent-solvent interactions. Nevertheless, the moderate number of water molecules required for successful simulations of the Raman spectra of aqueous thymine, suggests that the vibrational modes and derivatives of the polarizability of the solute are mainly locally influenced, while the effect of bulk water is rather modest.

The recently developed efficient protocol to explicit quantum mechanical modeling of structure and IR spectra of liquids and solutions (S. A. Katsyuba, S. Spicher, T. P. Gerasimova, S. Grimme, J. Phys. Chem. B 2020, 124, 6664) is applied to ionic liquid (IL) 1-ethyl-3-methylimidazolium bromide (EmimBr), its C2-deuterated analog [Emim-d]Br and its aqueous solutions. It is shown that the solvation strongly modifies frequencies and IR intensities of the CH/CD stretching vibrations (nu CH/nu CD) of the imidazolium ring. The main vibrational spectroscopic features of the neat IL are reproduced by the simulations for a cluster (EmimBr)9, in which all three imidazolium CH moieties of the solvated cation form short contacts with three Br- anions, and another two Br- anions are located on top and bottom of imidazolium ring. Cluster models of aqueous solutions reproduce the experimental vibrational frequencies of actual solutions, provided that the Br- anion of solvated contact ion pair (CIP) is situated on top of imidazolium ring, and CH/CD moieties of the latter participate in short contacts with surrounding water molecules. Both structural and spectroscopic analysis allow to interpret the short contacts CH/CD & ctdot;Br- and CH/CD & ctdot;OH2 as hydrogen bonds of approximately equal strength. Enthalpies of bonding of these liquid-state H-bonds, estimated with the use of empirical correlations, amount to ca. 1.4 kcal & sdot;mol-1, while the analogous estimates obtained for the gas-phase charged species [Emim]2Br+ increase to 5.6 kcal & sdot;mol-1. It is shown that formation of solvent-shared ion pair (SIP) in aqueous solution, where the counterions of IL are separated by two water molecules H-bonded to a Br- anion, produces frequency shifts Delta nu CH/CD, strongly different from the case of CIP formation. This difference can be used for IR/Raman spectroscopic differentiation of the type of solvated ion pairs of EmimBr or other related ILs. DFT calculations of vibrational spectra of cluster models of ionic liquid (IL) and its aqueous solutions accurately reproduce the experimental spectra. This suggests a close correspondence of the cluster models to actual neat and aqueous IL, and allows to distinguish spectral signatures of contact and solvent-shared ion pairs. image

This work presents the synthesis of a new representative of hemicurcuminoids with a nonyloxy substituent (HCur) as a fluorescent amphiphilic structural element of vesicular aggregates based on phosphatidylcholine (PC), phosphatidylserine (PS), and 10,12-pentacosadiynoic acid (PCDA). Both X-ray diffraction analysis of the single crystal and 1H NMR spectra of HCur in organic solvents indicate the predominance of the enol-tautomer of HCur. DFT calculations show the predominance of the enol tautomer HCur in supramolecular assemblies with PC, PS, and PCDA molecules. The results of the molecular modeling show that HCur molecules are surrounded by PC and PS with a rather weak exposure to water molecules, while an exposure of HCur molecules to water is enhanced under its supramolecular assembly with PCDA molecules. This is in good agreement with the higher loading of HCur into PC(PS) vesicles compared to PCDA vesicles converted into polydiacetylene (PDA) ones by photopolymerization. HCur molecules incorporated into HCur-PDA vesicles exhibit greater planarity distortion and hydration effect in comparison with HCur-PC(PS) ones. HCur-PDA is presented as a dual fluorescence-chromatic nanosensor responsive to a change in pH within 7.5–9.5, heavy metal ions and polylysine, and the concentration-dependent fluorescent response is more sensitive than the chromatic one. Thus, the fluorescent response of HCur-PDA allows for the distinguishing between Cd2+ and Pb2+ ions in the concentration range 0–0.01 mM, while the chromatic response allows for the selective sensing of Pb2+ over Cd2+ ions at their concentrations above 0.03 mM.

The photophysical properties of a series of D-π-A chromophores, where D is represented by di- or trialkylaniline moiety, π – vinylene, A - quinoxaline, quinoxalinone, quinoline, benzothiazole and thiophenecarboxaldehyde, have been analyzed upon acidification. In all cases, appearance of the second emission band is associated with protonation of the nitrogen atom in the donor fragment. Nevertheless, the simultaneous appearance of two emission bands at equal amounts of acid is observed only for dyes with a quinoxalinone acceptor fragment, which suggests the crucial role of the latter in providing dual emission upon acidification. The highest pH sensitivity has been achieved for the dye with an ethyl group at the ortho-position of benzene ring relative to the vinylene bridge. In contrast, the variation of substituents at the aniline nitrogen atom, the protonation of which causes the appearance of the emission under acidic conditions, does not lead to significant changes in pH sensitivity.

The recently developed efficient protocol for the explicit quantum mechanical modeling of the structure and IR spectra of liquids and solutions [Katsyuba et al., J. Phys. Chem. B, 2020, 124, 6664-6670] is used to describe aqueous solutions of cytosine. The same cluster model of a solute surrounded by the first solvation shell of solvent molecules was shown to be sufficient to reproduce experimental vibrational frequencies and relative IR and Raman intensities. An equally good quality of Raman spectra was provided by B3LYP-D3/def2-TZVP and B3LYP-D3/aug-cc-pVDZ simulations. Computations using the PBE functional were sufficient for modeling of the IR spectra but failed in the simulations of Raman scattering. It is shown that strong changes of frequencies and relative intensities of Raman and IR bands of cytosine, caused by its hydration, cannot be completely assigned to the influence of hydrogen bonds (HBs) with 7 or 8 closest water molecules. They are rather ascribed to the combined effect of solute-solute and solute-solvent HBs with the participation of at least 30 water molecules separating cytosine from the bulk solvent. This suggests that the vibrational modes and derivatives of the polarizability and dipole moment of the solute are mainly locally influenced by its first hydration shell, while the influence of bulk water is rather modest.

Chromophores with 2-methoxyphenyl-1(3)methylindolizine donor and tricyanofuran acceptor moiety linked by octatetraene n-bridge have been synthesized and their linear and nonlinear optical properties were investigated. Chromophores exhibited large solvatochromic shifts (∼100 nm) when passing from dioxane to DMSO solutions and their absorption maxima shifted from visible to near-IR region. An additional narrow intensive absorption band at ca. 921–954 nm appeared in DMSO solution resulting from the crossing of cyanine limit. Density functional theory was used to calculate the first hyperpolarizability (β) of the chromophores.

Implicit and explicit quantum mechanical modeling of solutions of a series of quinoxalinone-based hydrazones allowed to describe their tautomeric/isomeric/conformational composition and IR and UV-Vis spectra.

A series of dialkylaminostyrylhetarene dyes constructed from electron-rich and electron-deficient moieties of various structures connected via vinylene π-bridges are introduced as temperature-sensitive luminophores. The temperature dependent emission of the dyes in the acidified dichloromethane solutions derives from temperature-induced shift of the equilibrium between neutral and protonated forms of the dyes. The heating-induced blue shift and intensification of emission of neutral form of the dyes make them a promising basis for development of nanoparticles exhibiting temperature-sensitivity in aqueous solutions at pH typical of biological liquids. Hydrophobicity-driven incorporation of the water insoluble dyes into L-α-phosphatidylcholine(PC)-based bilayers allows to obtain water dispersible dye-PC aggregates, and to follow their emission in the aqueous solutions. Structure of the dyes has strong impact on the efficacy of the dyes incorporation into the PC-based bilayers, temperature sensitivity of emission of the dye-PC aggregates and its reversibility under the heating/cooling cycles. This enables structural optimization of the dyes in order to obtain the dye-PC species demonstrating maximal temperature dependence and reversibility of their luminescence in aqueous solutions. The selected leader exhibits low cytotoxicity exemplified for M-HeLa and Chang Liver cell lines, while the efficient cell internalization of the dye, manifested in the staining of the cell cytoplasm, opens further opportunities for biosensing applications.

The recently developed efficient protocol to explicit quantum mechanical modeling of the structure and IR spectra of liquids and solutions [Katsyuba et al., J. Phys. Chem. B, 2020, 124, 6664-6670] is applied to ionic liquid 1-ethyl-3-methyl-imidazolium tetrafluoroborate [Emim][BF4], and its C2-deuterated analog [Emim-d][BF4]. It is shown that the solvation strongly modifies the frequencies and IR intensities of both cationic and anionic components of the ionic liquids. The main features of the bulk spectra are reproduced by the simulations for cluster ([Emim][BF4])8, representing an ion pair solvated by the first solvation shell. The geometry of the cluster closely resembles the solid-state structure of the actual ionic liquid and is characterized by short contacts of all CH moieties of the imidazolium ring with [BF4]- anions. Both structural and spectroscopic analyses allow the contacts to be interpreted as hydrogen bonds of approximately equal strength. The enthalpies of these liquid-state H-bonds, estimated with the use of empirical correlations, amount to 1.2-1.5 kcal mol-1, while the analogous estimates obtained for the gas-phase charged species [Emim][BF4]2- and [Emim]2[BF4]+ increase to 3.6-3.9 kcal mol-1.

The recently developed efficient protocols to implicit [Grimme et al., J. Phys. Chem. A 125, 4039-4054 (2021)] and explicit quantum mechanical modeling of non-rigid molecules in solution [Katsyuba et al., J. Phys. Chem. B 124, 6664-6670 (2020)] are used to describe conformational equilibria of 1,2-dichloroethane and 1,2-dibromoethane in various media. Two approaches for evaluation of trans/gauche free energy differences, ΔGt-g, are compared: (a) direct ΔGt-g computation in implicit solution; (b) the use, together with experimental intensities, of infrared absorption coefficients and Raman scattering cross sections computed for each explicitly modeled solution. The same cluster model of a solute surrounded by the first solvation shell of solvent molecules was used to simulate both Raman and IR spectra. The good agreement between the two approaches indicates the reliability of both methods. The importance of using correct absorption coefficients and Raman scattering factors for each medium is discussed. The ΔGt-g estimates from both implicit and explicit solvation simulations were combined with experimentally measured enthalpy differences ΔHt-g available in the literature to obtain condensed-state ΔSt-g estimates.

1,3-Diketone calix [4]arene (CA) and thiacalix [4]arene (TCA), with the hydrophobic substituents introduced onto lower or upper rims respectively, form mixed aggregates with 10,12-pentacosadiynoic acid (PCDA) through the thin film hydration technique. Computer simulations, showing the arrangement of TCA and CA molecules in supramolecular clusters with PCDA molecules, suggest that PCDA assemblies with both cyclophanes are a convinient basis for the coordination of metal ions. However, photopolymerization of mixed aggregates reveals more disruption of the vesicular nanostructure of polydiacetylene (PDA) when CA molecules are included compared to TCA. The incorporation of the TCA and CA ligands influences the ability of the mixed PDA-bilayers to conformational and spectral changes and provides tight coordination of Tb3+ ions and efficient sensitizing of the Tb3+-centered luminescence. The PDA-bilayers incorporated by terbium TCA complex provide more sensitive response on the series of heavy metal ions vs their CA-based analogues. The surface exposed TCA rims and carboxylate moieties of PDA provide two different binding sites for Tb3+ and heavy metal ions. Both distribution of Tb(3+ )and heavy metal ions between these sites and heterometallic complex formation are revealed as the factors affecting the luminescence response of PDA-TCA terbium complex in the solutions of heavy metal ions. The interplay between these factors is the reason for the different luminescence response of PDA-TCA terbium complex on Cd2+, Hg2+ and Pb2+ ions. The PDA-vesicles incorporated by terbium TCA complex exhibit easier phase separation vs the PDA vesicles themselves, which favors the extraction of Pb2+ ions.

A synthetic method for a primary 2-(thiophen-2'-yl)ethylphosphine was developed. The reaction of thiophenylethylphosphine with paraformaldehyde and primary arylamines leads to the formation of cyclic bisphosphines, namely, 1,5-di(aryl)-3,7-bis(thiophenylethyl)-1,5-diaza-3,7-diphosphacyclooctane (aryl = phenyl, p-tolyl). The obtained bisphosphines form cationic bis-P,P-chelate complexes with copper(I) tetrafluoroborate, which were structurally characterized by NMR spectroscopy, mass spectrometry, and elemental and XRD analyses. Surprisingly, the copper(I) complexes display a multiband emission in the solid state with maxima at 355-360, 425-430, and 480-490 nm and nanosecond lifetimes (1.2-1.4 ns) upon a 335 nm excitation. The excitation of the complexes at 360 nm at room temperature results in a deep-blue emission at 425-430 nm and a tail at 460-490 nm. A temperature decrease leads to an increased intensity of the emission band at 480 nm, while the luminescence lifetimes insignificantly increased up to 14 ns. Quantum chemical calculations explain the observed unusual luminescent behavior by the existence of "undistorted" and "flattened" singlet excited states of copper(I) complexes at room temperature and at 77 K, respectively.