Phenyl Research Articles

Dicarbatriphyrin(2.1.1) and its Carbacalix[1]Phyrin Analogue: Structure-Property Relationships and Application as a Fe(III) Chemosensor.

The investigation of unsaturated or π-conjugated hydrocarbons, particularly within the macrocyclic framework, has garnered significant interest due to their fundamental properties and practical applications. This research focuses on the synthesis and characterization of a novel stable dicarbatriphyrin(2.1.1) which was constructed by amending the [14]triphyrin(2.1.1) framework by, replacing two pyrrole rings with meta-connected phenyl rings and introducing an o-benzene bridge at the C2 position. The structural modification resulted in a saddle-shaped macrocyclic core with negative Gaussian curvature, as confirmed by crystal structure analysis. This unique molecular topology offers acumens into the structure-property relationships in the curved locally π-conjugated contracted porphyrinoids. The macrocycle exhibits fluorescent emission in solution, which is selectively quenched by Fe(III) ions, highlighting its potential as a chemosensor for Fe(III) cations. Additionally, the formation of carbacalix[1]phyrin(2.1.1), a phlorin analogue of dicarbatriphyrin(2.1.1), which exhibits a chair conformation in contrast to the saddle-shaped structure of its oxidized counterpart. Remarkably, the emergence of a mono-pyrrolic calixbenziphyrin marks an unprecedented advancement in the field of calixphyrin chemistry. Moreover, theoretical studies provide strong support for the experimental findings, reinforcing the conclusions drawn from the structural and functional analyses.

Temperature dependence of structural evolution and fragility of glass-forming monohydroxy alcohols

The dynamic, structural, and thermodynamic properties of thirty-four monohydroxy alcohols with varying molecular architectures, including differences in alkyl chain length, OH group position, and presence/type of carbon ring, were investigated. Results of dielectric spectroscopy, temperature-modulated differential scanning calorimetry, and X-ray diffraction, were analyzed to verify correlations between the glass transition temperature (Tg), molar mass (M), boiling temperature (Tb), dynamic and thermodynamic fragility (mα and m), and the structurally related parameter (S). The collected data revealed that primary and secondary alcohols generally adhere to the correlations Tg ∝ M0.51 and Tb = 132 + 2.2Tg, while alcohols with phenyl ring deviate from these trends. Moreover, it was found that the changes in the width of the main diffraction peak normalized by the peak position ΔQM/QM over temperature scaled by Tg correspond to the variable m. However, the extent and course of this relationship varies across alcohols belonging to different structural groups. The weakest correlation and largest scatter between S and m occur for phenyl alcohols exhibiting the greatest structural heterogeneity. This study underscores the challenges of establishing universal correlations between physical variables within the diverse group of monohydroxy alcohols and emphasizes the importance of considering specific molecular features in predicting glass-forming behaviour.

Carbon-13 Hyperpolarization of α-Ketocarboxylates with Parahydrogen in Reversible Exchange.

Signal Amplification by Reversible Exchange (SABRE) is a relatively simple and fast hyperpolarization technique that has been used to hyperpolarize the α-ketocarboxylate pyruvate, a central metabolite and the leading hyperpolarized MRI contrast agent. In this work, we show that SABRE can readily be extended to hyperpolarize 13C nuclei at natural abundance on many other α-ketocarboxylates. Hyperpolarization is observed and optimized on pyruvate (P13C=17%) and 2-oxobutyrate (P13C=25%) with alkyl chains in the R-group, oxaloacetate (P13C=11%) and alpha-ketoglutarate (P13C=13%) with carboxylate moieties in the R group, and phenylpyruvate (P13C=2%) and phenylglyoxylate (P13C=2%) with phenyl rings in the R-group. New catalytically active SABRE binding motifs of the substrates to the hyperpolarization transfer catalyst-particularly for oxaloacetate-are observed. We experimentally explore the connection between temperature and exchange rates for all of these SABRE systems and develop a theoretical kinetic model, which is used to fit the hyperpolarization build-up and decay during SABRE activity.

The interplay between structural features and the efficiency of the energy transfer process in terbium complexes with triarylcyclopentadienyl ligands

Terbium and gadolinium complexes with triarylcyclopentadienyl ligands having electron-donating methoxy substituents in the ortho- (CpPh2Ar−o) and para- (CpPh2Ar−p) positions of one of the phenyl rings have been synthesized. Different structural types, including tetranuclear [{CpPh2Ar−oTb (THF)}2 (μ2-Cl)2(μ3-Cl)3K (THF)]2 (Tb1), [{CpPh2Ar−oTb}2 (μ2-Cl)2 (μ3-Cl)3K]2 (Tb3), [{(CpPh2Ar−oTb)2 (μ2-Cl)3}2 (μ2-Cl)2] (Tb5), [{CpPh2Ar−pTb (THF)}2 (μ2-Cl)2 (μ3-Cl)3K (THF)]2 (Tb6), binuclear [{CpPh2Ar−oTb (THF)Cl}2 (μ2-Cl)2] (Tb4), [{CpPh2Ar−pTb (THF)}2 (μ2-Cl)2 (μ3-Cl)3K (THF)]2 (Tb7), [CpPh2Ar−p2Tb (μ2-Cl) (μ3-Cl)K]2 (Tb8) and mononuclear [CpPh2Ar−o2TbCl] (Tb2) complexes have been obtained and confirmed by single crystal X-ray diffraction analysis. All designed terbium complexes exhibit high quantum yields of the photoluminescence (up to 65 %). The introduction of a methoxy group into one of the phenyl rings of the triarylcyclopentadienyl ligand leads to a more than twofold increase in the quantum yield of the terbium ion luminescence. The estimated values of radiative rate krad of the terbium ion vary in the range of 0.23–0.69 ms. The presence of the methoxy group as well as the mutual disposition of the phenyl rings promotes the appearance of an intraligand charge transfer states involved in the energy transfer process. Due to a lowering of the energy of the interconfigurational 4f −5d transitions caused by the relatively strong crystal field of the Cp ligand in bis(cyclopentadienyl) terbium complexes, the quantum yield of the photoluminescence is high at the short lifetimes of the 5D4 level of the terbium ion.

Effects of Ring Functionalization in Anthracene-Based Cyclophanes on the Binding Properties Toward Nucleotides and DNA.

Supramolecular recognition of nucleobases and short sequences is an emerging research field focusing on possible applications to treat many diseases. Controlling the affinity and selectivity of synthetic receptors to target desired nucleotides or short sequences is a highly challenging task. Herein, we elucidate the effect of substituents in the phenyl ring of the anthracene-benzene azacyclophane on the recognition of nucleoside triphosphates (NTPs) and double-stranded DNA. We show that introducing phenyl rings increases the affinity for NTPs 10-fold and implements groove and intercalation binding modes with double-stranded DNA. NMR studies and molecular modeling calculations support the ability of cyclophanes to encapsulate nucleobases as part of nucleotides.

Synergistic effects of graphene nanoparticles on the thermomechanical properties of PEEK-HNTs nanocomposites

In our previous study, we selected a 3% concentration (PH3) from various prepared PEEK-HNTs nanocomposites. Poly (ether ether ketone) (PEEK) is characterized by non-perfluorinated aromatic compounds with 1,4-disubstituted phenyl groups linked by carbonyl (––CO––) and ether (––O––) groups, offering exceptional thermal stability, mechanical strength, tribological properties, and chemical resistance at high temperatures. Halloysite nanotubes (HNTs) are known for their non-toxic, environmentally friendly, cost-effective properties, with tunable release and rapid adsorption rates. In this study, we prepared graphene nanoparticle (GNP) composites at three different concentrations while maintaining constant PH3 levels. The composites underwent comprehensive characterization using FTIR, TGA, DSC, SEM, and DMA techniques. Thermomechanical properties were evaluated using a universal testing machine. Results demonstrate significant enhancements in hardness, impact strength, elongation at break, tensile modulus, and flexural modulus, with the highest performance observed in the GNP-loaded 0.3% (PHG3) concentration. The synergistic effects of GNP fillers in PH3 are attributed to enhanced interfacial adhesion and favorable interactions with the polymer matrix.

Synthesis, Characterization, Bioactivity Evaluation, and POM/DFT/Docking Analysis of Novel Thiazolidine Derivatives as Potent Anticancer and Antifungal Agents

AbstractA series of 2,2′‐(1,4‐phenylene)bis(N‐substituted phenylthiazolidine‐4‐amide) derivatives, denoted as (A3–9), were synthesized, and characterized for their potential applications against prostate cancer cells (PC3), and Candida albicans fungi. These compounds incorporate various substituents on the phenyl ring such as 4‐NO2, 3‐NO2, 4‐COCH3, 4‐H, 4‐OCH3, 4‐OCH2CH3, and 4‐Cl. The chemical structures of these derivatives were confirmed by NMR, FTIR, and mass spectroscopy. Biological assays, utilizing the MTT assay for prostate cancer cells (PC3) and the disk diffusion assay for Candida albicans fungi, were conducted to evaluate the bioactivity of these compounds. The results revealed promising cytotoxic and antifungal activities. Specifically, compounds A3 (IC50=69.74±0.96), A4 (IC50=63.64±0.950), and A9 (IC50=57.14±0.88 μg/mL) exhibited notable potency against PC3 cells, while A7 and A8 exhibited considerable antifungal efficacy against Candida albicans with MIC of 312 μg/mL. Moreover, density functional theory (DFT) simulations were used to study electronic properties and reactivity descriptors such as energy gap (Eg), ionization potential (IP), electron affinity (EA), chemical potential (μ), chemical hardness (η), global softness (σ), electronegativity (χ), and electrophilicity (ω) to gain a better understanding of the Structure‐Activity Relationship (SAR). Molecular docking analysis against DNA Gyrase and EGFR tyrosine kinase enzymes revealed strong binding interactions of the investigated molecules within their active sites, making them valuable candidates for further development as therapeutic agents against prostate cancer and fungal infections. POM analysis indicates the presence of two antifungal pharmacophore sites (O1δ−, O2δ−) and (O3δ−, O4δ−), as well as two antitumor pharmacophore sites (O1δ−, NH1δ+) and (O4δ−, NH2δ+).

2‐Oxazoline‐Based Polymer for Pharmaceutical Products Adsorption in Aqueous Media

ABSTRACTWe present the synthesis and comprehensive evaluation of a novel 2‐oxazoline‐based polymer (polyPhOx) functionalized with phenyl groups, designed for the efficient adsorption of pharmaceutical contaminants from aqueous solutions. Employing living polymerization techniques (CROP) with two distinct initiators, we optimize reaction parameters including time, temperature, and initiator concentration. The rigorous characterization of the obtained polymer is depicted as well as the demonstration of its significant binding capacity for various pharmaceuticals, exploiting π–π and electrostatic interactions to achieve superior adsorption efficiency. Adsorption experiments are performed using high concentrations of model pharmaceuticals, including aspirin, ibuprofen, metoclopramide, pyramidone, oestradiol, and indomethacin, in hydroalcoholic solutions. Initial investigations confirm polyPhOx's exceptional efficacy, particularly with hydrophobic compounds such as oestradiol, achieving adsorption capacities of up to 56.67 mg g−1. Further validation in real environmental samples highlights the polymer's practical applicability, showing substantial removal rates even under complex matrix conditions and bringing hope for effective water purification solutions. Remarkably, polyPhOx retains high adsorption performance after 10 cycles, underscoring its potential for sustainable and cost‐effective water purification. This study not only introduces a promising material for environmental remediation but also demonstrates its robustness and reusability, paving the way for advanced wastewater treatment solutions targeting persistent pharmaceutical pollutants.

Comprehensive study of 1,2,4-triazolo[1,5]benzodiazepine derivatives: Synthesis, characterization, X-ray diffraction, DFT calculations, Hirshfeld surface analysis, ADMET properties, and molecular docking

In this research, the synthesis of triazolobenzodiazepine derivatives was achieved through a [3 + 2] cycloaddition reaction between N-(4-bromophenyl)-C-ethoxycarbonylnitrilimine and benzodiazepine 1. The structures of the products, denoted as 3 and 4, were determined using NMR spectroscopy (1H and 13C). However, only one single crystal, corresponding to compound 4, was successfully obtained. Single-crystal X-ray diffraction analysis of compound 4 confirms the proposed structure and accurately determines the stereochemistry, indicating that the styryl group at position 3a and the phenyl group at position 5 are on opposite sides. We compared the spectral data obtained from theoretical calculations with the experimental data. and found high correlation coefficients, indicating a satisfactory reproducibility of both the geometrical parameters and chemical shifts by the computational method used. Additionally, we used Hirshfeld surface analysis to explore the intermolecular interactions within the crystal lattice, providing further understanding of the molecular packing. Additionally, an ADMET study was performed to estimate its toxicity, excretion, metabolism, distribution, and absorption.

A promising class of Antiprotozoal agents, design and synthesis of novel Pyrimidine–Cinnamoyl Hybrids

Malaria, caused by parasitic protozoans of the Plasmodium genus, continues to be one of the greatest global health crises, especially in Africa. The emergence of antimalarial drug resistance continues to be a health problem necessitating an urgent need for alternative and cost-effective antimalarials. Using a molecular hybridization approach, we report the design and synthesis of an efficacious novel class of antiprotozoal agents; (E)-1-(4-(4,6-diphenylpyrimidin-2-yl)piperazin-1-yl)-3-phenyl prop-2-en-1-one derivatives (8a-r). The in vitro inhibitory activity of the synthesized compounds was evaluated against the NF54 chloroquine-sensitive strain of Plasmodium falciparum. From the antiprotozoal screening, three compounds displayed propitious activity with IC50 values (0.18-0.21μM), using quinine and chloroquine as standard antimalarials. Compounds 8o and 8l emerged as the most potent candidates with IC50 values of 0.18 ± 0.02 μM and 0.21 ± 0.001 μM with an associated good safety index of 18.59 and 16.75 to human kidney epithelial (HEK293) cells, respectively. The synthesized analogues present a new chemical architecture structurally unrelated to the current regime of antimalarial drugs, representing a valid strategy to combat resistance in P. falciparum species to current commercial drugs. We further investigated the binding affinities of the compounds against recombinant forms of two P. falciparum heat shock protein 70 homologues; PfHsp70-1 and PfHsp70-z, both of which are essential and promising druggable candidates. Compound 8l exhibited the highest binding affinity for both PfHsp70s. Furthermore, molecular docking revealed that compounds 8k, 8l, 8m, and 8o exhibited better fitness to PfHsp70-1, with compounds 8l and 8o showing the highest binding affinity of 10.5 kcal/mol and 10.1 kcal/mol, respectively. Therefore, it can be speculated that PfHsp70-1 may be a possible target of some of the inhibitors tested in this study. The presence of electron-donating groups on the phenyl ring of 4,6-pyrimidine moiety and cinnamoyl group demonstrated a positive correlation between the observed computational data and the biological activity. Taken together, this paper demonstrates the importance of using the molecular hybridization approach in the development of newer cinnamoyl clubbed with 4,6-diphenyl pyrimidine hybrids as potential antiprotozoal agents.

Exploring Acyl Thiotriazinoindole Based Pharmacophores: Design, Synthesis, and SAR Studies with Molecular Docking and Biological Activity Profiling against Urease, α-amylase, α-glucosidase, Antimicrobial, and Antioxidant Targets.

A diminutive chemical library of acyl thiotriazinoindole (ATTI) based bioactive scaffolds was synthesized, instigated by taking the economical starting material Isatin, through a series of five steps. Isatin was first nitrated followed by the attachment of pentyl moiety via nucleophilic substitution reaction. The obtained compound was reacted with thiosemicarbazide to obtain thiosemicarbazone derivative, which was eventually cyclized using basic conditions in water as solvent. Finally, the reported series was obtained through reaction of nitrated thiotriazinoindole moiety with differently substituted phenacyl bromides. The synthesized compounds were characterized using NMR spectroscopy and elemental analysis. Finally, the synthesized motifs were scrutinized for their potential to impede urease, α-glucosidase, DPPH, and α-amylase. Compound 5h with para cyano group manifested the most pivotal biological activity among all, displaying IC50 values of 29.7 ± 0.8, 20.5 ± 0.5 and 36.8 ± 3.9µM against urease, α-glucosidase, and DPPH assay, respectively. Simultaneously, for α-amylase compound 5g possessing a p-CH3 at phenyl ring unfolded as most active, with calculated IC50 values 90.3 ± 1.1µM. The scaffolds were additionally gauged for their antifungal and antibacterial activity. Among the tested strains, 5d having bromo as substituent exhibited the most potent antibacterial activity, while it also demonstrated the highest potency against Aspergillus fumigatus. Other derivatives 5b, 5e, 5i, and 5j also exhibited dual inhibition against both antibacterial and antifungal strains. The interaction pattern of derivatives clearly displayed their SAR, and their docking scores were correlated with their IC50 values. In molecular docking studies, the importance of interactions like hydrogen bonding was further asserted. The electronic factors of various substituents engendered variety of interactions between the ligands and targets implying their importance in the structures of the synthesized heterocyclic scaffolds. To conclude, the synthesized compounds had satisfactory biological activity against various important targets. Further studies are therefore encouraged by attachment of different substitutions in the structure at various positions to enhance the activity of these compounds.

A multi-computational and crystallographic investigation for the antibiotic mechanism of two 2,4-bis(4-methoxyphenamino)pyrimidines

2,4-bis(4-methoxyphenamino)pyrimidines are effective anti-bacterial against various bacteria. The compounds 1a and 1b displayed IC50 values of 3µM and 6.1µM, respectively, against Salmonella Typhimurium. The research aims to comprehensively understand the mechanisms of action of these compounds against bacteria using a diverse array of experimental and computational techniques. The findings from the single-crystal X-ray crystallographic investigation reveal several key insights. First, compounds 1a and 1b adopt distinct conformations of the same structure. Second, the amine-pyrimidine resonance is favored over the amine-methoxy aryl resonance. Third, H⸱⸱⸱H, O⸱⸱⸱H, and N⸱⸱⸱H interactions are the primary driver of molecular assembly. Lastly, Van der Waals and hydrophobic interactions significantly influence the crystal architecture and are conformation-dependent. Computational results suggest that, depending upon the molecular volume, both compounds can inhibit SseF with a marginal difference by stable binding with the same conformer observed in the solid state of 1a through hydrophobic interactions due to the presence of electron-rich phenyl rings. The compound 1b exhibited greater structural variability in the binding site compared to 1a, leading to lower stability. Moreover, the higher molecular volume of 1b, attributed to the methyl group, results in its comparatively lesser fitting in the SseF pore compared to 1a.

Quercetin analogues of kojic acid as strong antioxidant derivatives: Theoretical insights

Kojic acid is a natural product produced by many fungal species and has a wide range of applications. The chelating and antioxidant capacity are associated with their chemical and biological properties. In this study, some molecular modifications were proposed and substituted and hydroxylated phenyl moieties were introduced in the basic structure of kojic acid. The antioxidant capacities were calculated by DFT/B3LYP/6-311++G(2d,2p). Different antioxidant mechanisms were considered such as frontier molecular orbitals (HOMO, LUMO, and GAP), electron (IP, SET, and SPLET), or hydrogen transfers (BDEOH and HAT) on gas phase and PCM methods. The phenyl increases the antioxidant capacity, especially when an electron donating group (EDG) is found at the para position of the phenyl ring when compared to electron withdrawing groups (EWGs), for all studied mechanisms. The chemical stability agrees with spin density contributions for their cationic free radicals and semiquinones. A structural similarity between hydroxylated derivatives of kojic acid and quercetin was observed on gas phase and water. The lower BDEOH values ​​at the phenol positions are more important for the antioxidant capacity than at the enol position. Phenolic semiquinones are more stables than enolic ones. The chemical stability depends on the number of resonance structures and the positions where the unpaired electron can be found with the highest contributions. In conclusion, phenyl substitution is a valuable molecular modification for the increase on antioxidant capacity of kojic acid. Quercetin analogues of kojic acid were proposed as strong antioxidant derivatives.

Rational design, synthesis, computational studies and biological evaluation of new diazepanone derivatives: Crystal structure of 2,7-bis(4-chlorophenyl)-1,3-dimethyl-1,4-diazepan-5-one

Structural and biological evaluation of newly designed and synthesized diazepanone derivatives (3a-c) with modified functionalities is reported in this paper, as liponucleoside class of antibiotics possessing 1,4-diazepanone as core moiety are under investigation since last decade to improvise their drug action. FT-IR, HR-ESI-MS, 1H NMR and 13C NMR spectral studies are used for the structural characterization of synthesized compounds (3a-c). 1H NMR spectral data reveal that the diazepanone ring exhibits chair conformation in solution state. The solid state geometry for compound 3a acquired by SC-XRD study also in favour of chair conformation of the diazepanone ring with equatorial orientation of all the substituents. Comparison of experimental bond parameters with theoretical results attained by DFT studies using B3LYP/6–311G++ (d,p) basis set are in good agreement. Molecular electrostatic potential surface (MEPS) and HOMO-LUMO energies are used to elucidate the topology and physicochemical parameters of 3a. Nature of crystal packing is ascertained by Hirshfeld surface and its delineated 2D-Fingerprint plot in addition with the SC-XRD evidences. Antibacterial evaluation of (3a-c) against tested bacterial strains reveals that the compounds have remarkable antibacterial potencies compared to tested standard drug. Among the compounds 3a-c, the compound 3c with fluoro-substitution on the phenyl ring shows highest activity.

Homochiral “8″-shaped nanotoroids assembled from polypeptides

Figure eight-shaped (“8″-shaped) nanotoroids have been observed in DNA and proteins, however, they are rarely reported in synthetic polymer systems. Reported here is the formation of homochiral “8″-shaped nanotoroids from poly(γ-benzyl glutamate) (PBG) homopolymers. The L-type and D-type PBGs, i.e., PBLG and PBDG respectively, form left-handed and right-handed “8″-shaped chiral nanotoroids. The formation of the nanotoroids is achieved in a two-step route. Nanofibers are first self-assembled by the PBG homopolymers, which, with changing solvent nature, break into short nanofibers and twist into “8″-shaped nanotoroids. In such processes, the pendant phenyl groups of PBGs change from an extended to a contract form, which generates the internal stress driving the transition of nanofibers to “8″-shaped nanotoroids. This work not only enriches the topology and preparation method of nanotoroids, but also enhances our ability in controlling polymer nanostructures.

Structure of 2,3,5-tri-phenyl-tetra-zol-3-ium chloride hemi-penta-hydrate.

The title hydrated mol-ecular salt, C19H15N4 +·Cl-·2.5H2O, has two tri-phenyl-tetra-zolium cations, two chloride anions and five water mol-ecules in the asymmetric unit. The cations differ in the conformations of the phenyl rings with respect to the heterocyclic core, most notably for the C-bonded phenyl ring, for which the N-C-C-C torsion angles differ by 36.4 (3)°. This is likely a result of one cation accepting an O-H⋯N hydrogen bond from a water mol-ecule [O⋯N = 3.1605 (15) Å], while the other cation accepts no hydrogen bonds. In the extended structure, the water mol-ecules are involved in centrosymmetric (H2O)2Cl2 rings as well as (H2O)4 chains. An unusual O-H⋯π inter-action and weak C-H⋯O and C-H⋯Cl hydrogen bonds are also observed.

Phenyl Radical Activates Molecular Hydrogen Through Protium and Deuterium Tunneling.

Activating dihydrogen, H2, is a challenging endeavor typically achieved using transition metal centers. Pure main group compounds capable of this are rare and have emerged in recent decades. These systems rely on synergistic donor-acceptor interactions with H2's antibonding σ* and bonding σ orbital. An alternative (hydrocarbon) radical-mediated activation is problematic, because the H-H bond is stronger (104.2kcalmol-1) than most C-H bonds. Here, we explore using the phenyl radical to tackle this, forming benzene with a C-H bond energy (112.9 kcal mol-1) that provides a thermodynamic driving force. We mainly observe a benzene-HI complex upon photolysis of iodobenzene in an H2-doped neon matrix at 4.4 K despite a barrier of 7.6kcalmol-1, while phenyl radical forms in case of the heavier D2 isotopologue. When D2 molecules are allowed to diffuse, mono-deuterated benzene accumulates within hours. Computations using path integral-based instanton theory highlight that primarily the transferred hydrogen atom is moving during the reaction which greatly increases the tunneling probability. In excellent agreement with the experimental results, we predict significant tunneling rate constants for both isotopologues, H2 and D2, featuring a strong kinetic isotope effect of up to four orders of magnitude at the lowest temperatures.

β-Cyclodextrin Catalyzed, One-Pot Multicomponent Synthesis and Antimicrobial Potential of N-Aminopolyhydroquinoline Derivatives.

In the present report, we have described the synthesis of N-aminopolyhydroquinoline (N-PHQ) derivatives using highly efficient β-cyclodextrin (β-CD) as a catalyst by the Hantzsch condensation of substituted aromatic aldehydes, dimedone, and hydrazine hydrate in one pot. The reactions were completed in a shorter time without the generation of any other byproduct. The synthesized N-PHQs were washed thoroughly with distilled water and recrystallized with ethanol to get highly purified products (as crystals). The structure of the synthesized N-PHQs was established by using advanced spectroscopic techniques like FT-IR, NMR (1H, 13C, DEPT, COSY, and HSQC), ESI-MS, and Elemental Analyzer. The N-PHQs derivatives demonstrated moderate to excellent resistance against the tested strains (both fungal as well as bacterial). The presence of polar groups, which are able to form H-bonds, attached to the phenyl ring like -NO2 (4b and 4c), and -OMe (4i, 4j, and 4k) exhibits excellent activity, which is comparable to standard drugs, amoxicillin and fluconazole.

Origin of Intersystem Crossing in Red-Light Absorbing Bodipy Derivatives: Time-Resolved Transient Optical and Electron Paramagnetic Resonance Spectral Studies with Twisted and Planar Compounds.

We studied the intersystem crossing (ISC) property of red-light absorbing heavy atom-free dihydronaphtho[b]-fused Bodipy derivatives (with phenyl group attached at the lower rim via ethylene bridge, taking constrained geometry, i.e., BDP-1 and the half-oxidized product BDP-2) and dispiroflourene[b]-fused Bodipy (BDP-3) that have a twisted π-conjugated framework. BDP-1 and BDP-3 show strong and sharp absorption bands (i.e., ε = 2.0 × 105 M-1 cm-1 at 639 nm, fwhm ∼491 cm-1 for BDP-3). BDP-1 is significantly twisted (φ = 21.6°), while upon mono-oxidation, BDP-2 becomes nearly planar on the oxidized side (φ = 3.5°). Interestingly, BDP-2 showed efficient ISC (triplet state quantum yield, ΦT = 40%) due to S1/T2 state energy matching. Long-lived triplet excited state was observed (τT = 212 μs in solution and 2.4 ms in polymer matrix), and ISC takes 4.0 ns. Differently, twisted BDP-1 gives weak ISC only 5%, ISC takes 7.7 ns, and the triplet state is populated only with addition of ethyl iodide. Time-resolved electron paramagnetic resonance spectra of BDP-1 revealed the coexistence of two triplet states, with drastically different zero-field splitting D parameters of -2047 MHz and -1370 MHz, respectively, along with varying sublevel population ratios. We demonstrate that the ISC is not necessarily enhanced by torsion of the π-conjugation framework; instead, S1/Tn state energy matching is more efficient to induce ISC even in compounds that have planar molecular structures.

Switching Sides: Regiochemistry and Functionalization Dictate the Photoswitching Properties of Imines.

Photoswitchable imines demonstrate light-dependent dynamic covalent chemistry and can function as molecular ratchets. However, the design of aryliminopyrazoles (AIPs) has been limited to N-pyrazole derivatives with ortho-pyrrolidine motifs. The impact of other functionalization patterns on the photoswitching properties remains unknown. Here, we present a systematic structure-property analysis and study how the photoswitching properties can be tuned through ortho- and para-functionalization of the phenyl ring in N-pyrazole and N-phenyl AIPs. This study establishes the first set of design rules for these AIP photoswitches and reports the most stable Z-isomer of an AIP to date, enabling its crystallization and resulting in the first reported crystal structure of a metastable Z-aldimine. Finally, we demonstrate that the AIPs are promising candidates for photoswitching in the condensed phase.