Revisiting Biginelli-like reactions: solvent effects, mechanisms, biological applications and correction of several literature reports.

This study critically reevaluates reported Biginelli-like reactions using a Kamlet-Abboud-Taft-based solvent effect model. Surprisingly, structural misassignments were discovered in certain multicomponent reactions, leading to the identification of pseudo three-component derivatives instead of the expected MCR adducts. Attempts to replicate literature conditions failed, prompting reconsideration of the described MCRs and proposed mechanisms. Electrospray ionization (tandem) mass spectrometry, NMR, melting points, elemental analyses and single-crystal X-ray analysis exposed inaccuracies in reported MCRs and allowed for the proposition of a complete catalytic cycle. Biological investigations using both pure and "contaminated" derivatives revealed distinctive features in assessed bioassays. A new cellular action mechanism was unveiled for a one obtained pseudo three-component adduct, suggesting similarity with the known dihydropyrimidinone Monastrol as Eg5 inhibitors, disrupting mitosis by forming monoastral mitotic spindles. Docking studies and RMSD analyses supported this hypothesis. The findings described herein underscore the necessity for a critical reexamination and potential corrections of structural assignments in several reports. This work emphasizes the significance of rigorous characterization and critical evaluation in synthetic chemistry, urging a careful reassessment of reported synthesis and biological activities associated with these compounds.

Sensitive hydrazine detection and quantification with a fluorescent benzothiadiazole sensor: selective lipid droplets and in vivo imaging.

In this work, we describe the design, synthesis, characterization, photophysical evaluation, DFT calculations, and application of two novel fluorescent benzothiadiazole (BTD) sensors for hydrazine detection and quantification at the cellular and multicellular (in vivo) levels. The two probes were fully characterized, and their photophysical properties were evaluated. We tested the designed fluorogenic dye (named BTD-CHO) as a selective sensor for the rapid, sensitive, and selective detection of hydrazine. When treated with N2H4, the probe affords a new derivative named BTD-HZN, releasing water as the only byproduct. BTD-CHO exhibited a preference for lipid droplets (LDs) and accumulated inside these organelles. Hydrazine detection in LDs could be carried out by the in situ formation of BTD-HZN inside live cells. We efficiently visualized the lipids of a challenging cellular model, microalgae (Chlorella sorokiniana), using these sensors. In vivo experiments indicated rapid and efficient detection of the analyte using C. elegans and zebrafish (Danio rerio) as the multicellular models.

Deciphering the Dynamics of Organic Nanoaggregates with AIEE Effect and Excited States: Lipophilic Benzothiadiazole Derivatives as Selective Cell Imaging Probes.

An aggregation-induced emission enhancement (AIEE) effect in fluorescent lipophilic 2,1,3-benzothiadiazole (BTD) derivatives and their organic nanoaggregates were studied. A set of techniques such as single-crystal X-ray, dynamic light scattering (DLS), electron paramagnetic resonance (EPR), UV-vis, fluorescence, and density functional theory (DFT) calculations have been used to decipher the formation/break (kinetics), properties, and dynamics of the organic nanoaggregates of three BTD small organic molecules. An in-depth study of the excited-state also revealed the preferential relaxation emissive pathways for the BTD derivatives and the dynamics associated with it. The results described herein, for the first time, explain the formation of fluorescent BTD nanoaggregate derivatives and allow for the understanding of their dynamics in solution as well as the ruling forces of both aggregation and break processes along with the involved equilibrium. One of the developed dyes could be used at a nanomolar concentration to selectively stain lipid droplets emitting an intense and bright fluorescence at the red channel. The other two BTDs could also stain lipid droplets at very low concentrations and were visualized preferentially at the blue channel.

Plasma membrane imaging with a fluorescent benzothiadiazole derivative.

This work describes a novel fluorescent 2,1,3-benzothiadiazole derivative designed to act as a water-soluble and selective bioprobe for plasma membrane imaging. The new compound was efficiently synthesized in a two-step procedure with good yields. The photophysical properties were evaluated and the dye proved to have an excellent photostability in several solvents. DFT calculations were found in agreement with the experimental data and helped to understand the stabilizing intramolecular charge-transfer process from the first excited state. The new fluorescent derivative could be applied as selective bioprobe in several cell lines and displayed plasma-membrane affinity during the imaging experiments for all tested models.

The influence of the configuration of the (C70)2 dimer on its rovibrational spectroscopic properties: a theoretical survey.

A study of the spectroscopic properties of the buckyball dimer (C70)2 was performed, which involved mapping the potential energy curve of this system. The spectroscopic constants of the system were obtained using theoretical Dunham and discrete variable representation methods, as well as the Rydberg analytical function expanded to the sixth degree. Because the fullerenes in the dimer have both hexagonal and pentagonal faces, the properties of (C70)2 were examined for different system configurations. The fullerene dimerization process involves a weak interaction, possibly mediated by short-range components such as van der Waals forces. The differences between the spectroscopic constants of the various (C70)2 configurations and between their dissociation energies De were found to be rather small, which can be attributed to the dominant influence of the hexagonal faces of the fullerenes on the interaction between the fullerenes. These results should aid our understanding of the process of fullerene dimer formation and hopefully facilitate the development and application of new materials based on these dimers. Graphical Abstract Comparison of the potential energy curve and a schematic representation for the all (C70)2 fullerenes dimers configurations.

A novel analytical potential function for dicationic diatomic molecular systems based on deformed exponential function.

In this paper, we propose a new alternative analytical function aiming to better describe the potential energy curves of the doubly charged diatomic molecules. To achieve this goal, we modified an existing potential function in the literature to describe dicationic diatomic molecules using the deformed exponential function. We generated the potential energy curve of the testing group of dicationic diatomic molecules [Formula: see text], BH2+, [Formula: see text] and NH2+ by means of the CCSD(T)/aug-cc-pVQZ level of theory. To validate this new function, we also calculated the spectroscopic constants and the rovibrational spectra for the electronic state [Formula: see text]of the [Formula: see text] and [Formula: see text] systems using the Dunham and discrete variable representation methods. For BH2+ and NH2+ molecules, despite exhibiting a local minimum in the potential energy curve, no vibrational levels are supported, so the spectroscopic constants for these poorly bound systems are invalidated. The fitting accuracy had a better performance over the original potential for describing dicationic diatomic systems, considering that the discrete variable representation method resulted in a similar vibrational structure described in the literature. This fact can be explained due to the deformed function's flexibility.

Rovibrational spectroscopic constants of the interaction between ammonia and metallo-phthalocyanines: a theoretical protocol for ammonia sensor design.

In the present contribution, we develop an adapted theoretical approach based on DFT calculations (B3LYP functional) and solution of the nuclear Schrödinger equation by using the Discrete Variable Representation method to model the interaction of ammonia with metallo-phthalocyanines (MPcs, where M = Fe2+, Co2+, Ni2+, Cu2+ or Zn2+). This approach is intended to be a general protocol for the rational design of chemical sensors. The as-obtained binding energy curves, obtained from ab initio points, permitted us to calculate rovibrational energies and spectroscopic constants, as well as to establish the relative population of rovibrational states in different types of MPc-NH3 thermodynamic systems. Simulated binding energy curves show that the binding energy in MPc-NH3 systems is dependent on the type of M central ion, decreasing in the order FePc > ZnPc > CoPc > CuPc > NiPc, with values spanning from -170 to -16 kJ mol-1. Also, MPc-NH3 systems have at least 16 rovibrational levels, which confirms that they are all bound systems (chemically or physically). Despite that, only the interaction between ammonia and FePc, CoPc or ZnPc is spontaneous within the studied temperature range (200-700 K). NiPc and CuPc show a change between spontaneous and non-spontaneous behaviours at ∼400 K and ∼500 K, respectively. Less bound systems should more efficiently guarantee the sensors' signal reset, while they are also less specific than sensors built with medium to strongly bound systems. Moreover, the intermediate energy and spontaneous binding of ammonia to NiPc and CuPc at operation temperatures, as determined with our theoretical approach, suggests that these MPcs are most promising for ammonia sensors.

Effect of the crystalline environment on the third-order nonlinear optical properties of L-arginine phosphate monohydrate: a theoretical study.

A supermolecular approach combined with an iterative electrostatic scheme was employed to investigate the nonlinear optical properties of the hybrid L-arginine phosphate monohydrate crystal, the procedure being aided by DFT calculations. The supermolecular scheme basically treated the molecules surrounding the unit cell as point charges; this approximation results in rapid convergence, making it a feasible method. DFT functionals of different flavors were considered: B3LYP, B2PLYP, CAM-B3LYP, ωB97, and M06HF, utilizing the 6-311 + G(d) basis set. All functionals gave sufficiently accurate values for the dipole moment (µ) with respect to the experimental value 32(2) D. For the average linear polarizability ([Formula: see text]) and the total first hyperpolarizability (ß tot), good agreement was observed between the DFT-calculated values and MP2-derived results reported in the literature. For the second hyperpolarizability, both static and dynamic regimes were considered. The point-charge embedding approach led to an attenuation of the second hyperpolarizability γ for all frequencies considered. Excitations of γ were not observed for frequencies smaller than 0.1 a.u. For the second hyperpolarizability (both static and dynamic), computational results showed that L-arginine phosphate monohydrate exhibits a large nonlinear optical effect, which implies the occurrence of microscopic third-order NLO behavior.

Fully relativistic rovibrational energies and spectroscopic constants of the lowest X:(1)0(+)g, A':(1)2( u ), A:(1)1 ( u ), B':(1)0(-)u and B:(1)0(+)u states of molecular chlorine.

The main goal of this paper is to present the rovibrational energies and spectroscopic constants of the Cl(2) molecular system in the relativistic states [Formula: see text], A':(1)2( u ), A:(1)1( u ), [Formula: see text] and [Formula: see text]. More precisely, we have evaluated the Cl(2) ω ( e ), ω ( e ) x ( e ), ω ( e ) y ( e ), α ( e ), γ ( e ) and B ( e ) rovibrational spectroscopic constants using two different procedures. The first was obtained by combining the rovibrational energies, calculated through solving Schrödinger's nuclear equation and the diatomic rovibrational energy equation. The second was obtained by using the Dunham method. The calculated properties are in good agreement with available experimental data.