A Phosphine-Free Air-Stable Mn(II)-Catalyst for Sustainable Synthesis of Quinazolin-4(3H)-ones, Quinolines, and Quinoxalines in Water.

The synthesis, characterization, and catalytic application of a new phosphine-free, well-defined, water-soluble, and air-stable Mn(II)-catalyst [Mn(L)(H2O)2Cl](Cl) ([1]Cl) featuring a 1,10-phenanthroline based tridentate pincer ligand, 2-(1H-pyrazol-1-yl)-1,10-phenanthroline (L), in dehydrogenative functionalization of alcohols to various N-heterocycles such as quinazolin-4(3H)-ones, quinolines, and quinoxalines are reported here. A wide array of multisubstituted quinazolin-4(3H)-ones were prepared in water under air following two pathways via the dehydrogenative coupling of alcohols with 2-aminobenzamides and 2-aminobenzonitriles, respectively. 2-Aminobenzyl alcohol and ketones bearing active methylene group were used as coupling partners for synthesizing quinoline derivatives, and various quinoxaline derivatives were prepared by coupling vicinal diols and 1,2-diamines. In all cases, the reaction proceeded smoothly using our Mn(II)-catalyst [1]Cl in water under air, affording the desired N-heterocycles in satisfactory yields starting from cheap and readily accessible precursors. Gram-scale synthesis of the compounds indicates the industrial relevance of our synthetic strategy. Control experiments were performed to understand and unveil the plausible reaction mechanism.

Selective Low-Level Detection of a Perilous Nitroaromatic Compound Using Tailor-Made Cd(II)-Based Coordination Polymers: Study of Photophysical Properties and Effect of Functional Groups.

Three coordination polymers (CPs 1-3) are prepared based on diverse electron-donating properties and coordination arrangements of conjugated ligands. Interestingly, this is also reflected in their photophysical properties. The distinguishable high emissive nature of the luminescent coordination polymer shows its potentiality toward the detection of the perilous substance 2,4,6-trinitrophenol (TNP) or picric acid (PA). TNP has a higher propensity among explosive nitroaromatic compounds (epNACs) due to its significant π···π interaction with the free benzene moieties present in the CPs. Among CPs 1-3, 2 exhibits the highest sensitivity and selectivity toward TNP because of the most favorable π-π stacking with the conjugated organic linker. The calculated limit of detection (LOD) and corresponding quenching constant (KSV) from the Stern-Volmer (SV) plot for 1, 2, and 3 are found to be 0.68 µM and 7.49 × 104 M-1, 0.41 µM and 8.01 × 104 M-1, and 1.18 µM and 8.1 × 104 M-1, respectively. The fluorescence quenching mechanism is also highly influenced by their structure and coordination arrangement.

A Singlet-Diradical Co(III)-Dimer as a Nonvolatile Resistive Switching Device: Synthesis, Redox-Induced Interconversion, and Current-Voltage Characteristics.

Herein we report a ligand-centered redox-controlled strategy for the synthesis of an unusual binuclear diradical cobalt(III) complex, [Co2III(L•3-)2] (1), featuring two three-electron reduced trianionic monoradical 2,9-bis(phenyldiazo)-1,10-phenanthroline ligands (L•3-) and two intermediate-spin cobalt(III) centers having a Co-Co bond. Controlled ligand-centered oxidation of 1 afforded two mononuclear complexes, [CoII(L•-)(L0)]+ ([3])+ and [CoII(L0)2]2+ ([2]2+), which upon further ligand-centered reduction yielded a di-azo-anion diradical complex, [CoII(L•-)2] (4). In complex 1, two three-electron reduced di-azo-anion monoradical ligands (L•3-) bridge two intermediate Co(III) centers at a distance of 2.387(2) Å, while upon oxidation, one of the coordinating azo-arms of L becomes pendent, and in complexes [2]2+, [3]+, and 4, two tetradentate ligands coordinate a single Co(II) center in a tridentate meridional fashion with one uncoordinated azo-arm from each of the ligands. In the presence of reducing agents, the monomers [2]2+, [3]+, and 4 undergo ligand-centered reduction to form azo-anion radicals, and the otherwise pendent azo-arms in the presence of cobalt(II)-salts like Co(ClO4)2 or CoCl2 bind the second Co(II)-ion; further internal electron transfer from the cobalt center to the arylazo backbone produces the binuclear complex 1. Spectroscopic analysis, DFT studies, and control experiments were performed to understand the electronic structures and the ligand-centered redox-controlled interconversion. The application of complex 1 as a molecular memory device (memristor) was also explored. Complex 1 showed encouraging results as a memristor with a current ON/OFF ratio > 104 and is highly promising for resistive RAM/ROM applications.

Instigating the In Vitro Anticancer Activity of New Pyridine-Thiazole-Based Co(III), Mn(II), and Ni(II) Complexes: Synthesis, Structure, DFT, Docking, and MD Simulation Studies.

The perchlorate salt of (4-(4-methoxy phenyl)-2-(2-(1-pyridine-2-yl)ethylidene)hydrazinyl)thiazole (PytH·ClO4) and its metal perchlorate derivatives, namely, [Co(Pyt)2]ClO4 (1), [Mn(PytH)2](ClO4)2 (2), and [Ni(PytH)2](ClO4)2 (3), have been synthesized and characterized through single X-ray crystallography and spectroscopic methods. The ligand crystallizes in a space group P21/n in a nearly planar structure. The overall geometry of the complex salts is described as a distorted octahedron with a MN6 chromophore. The ligand (PytH·ClO4) behaves as a neutral N,N,N-tridentate donor toward the "soft" Mn(II) and Ni(II) centers, whereas the deprotonated ligand stabilizes the "hard" Co(III) center. The DNA binding constant (Kb) values of PytH·ClO4, 1, 2, and 3 are determined using the UV-vis spectroscopic method, and the Kb values are 9.29 × 105, 7.11 × 105, 8.71 × 105, and 7.82 × 105 mol-1, respectively, indicating the intercalative mode of interactions with CT-DNA. All the derivatives show effective antiproliferative activity against U-937 human monocytic tumor cells with IC50 values 4.374 ± 0.02, 5.583 ± 0.12, 0.3976 ± 0.05, and 11.63 ± 0.01 µM for PytH·ClO4, 1, 2, and 3, respectively. The best apoptosis mode of cell death is shown by 2 followed by PytH·ClO4 and 1 at an equivalent concentration of IC50 values. The combined molecular docking and dynamics simulation study evaluates the binding energies of anticancer agents, providing groove binding property with DNA. The 20 ns molecular dynamics simulation study reveals the maximum DNA binding stability of 2 corroborating the experimental results. The new class of metal derivatives of pyridine-thiazole can be used for advanced cancer therapeutics.

Solubilities of Amino Acids in Aqueous Solutions of Chloride or Nitrate Salts of Divalent (Mg2+ or Ca2+) Cations.

The solubilities of glycine, l-leucine, l-phenylalanine, and l-aspartic acid were measured in aqueous MgCl2, Mg(NO3)2, CaCl2,, and Ca(NO3)2 solutions with concentrations ranging from 0 to 2 mol/kg at 298.2 K. The isothermal analytical method was used combined with the refractive index measurements for composition analysis guaranteeing good accuracy. All salts induced a salting-in effect with a higher magnitude for those containing the Ca2+ cation. The nitrate anions also showed stronger binding with the amino acids, thus increasing their relative solubility more than the chloride anions. In particular, calcium nitrate induces an increase in the amino acid solubility from 2.4 (glycine) to 4.6 fold (l-aspartic acid) compared to the corresponding value in water. Amino acid solubility data in aqueous MgCl2 and CaCl2 solutions collected from the open literature were combined with that from this work, allowing us to analyze the relations between the amino acid structure and the salting-in magnitude.

Multifunctional Ni(II)-Based Metamagnetic Coordination Polymers for Electronic Device Fabrication.

The combination of two 8-aminoquinoline-based Schiff base ligands (L1 and L2) with SCN- and Ni(II) has led to the synthesis of two new one-dimensional thiocyanato-bridged coordination polymers: [Ni(L1)(NCS)2]n (1) and [Ni(L2)(NCS)2]n (2). Both compounds are isostructural and consists of regular zigzag thiocyanato-bridged chains with very weak S···S interchain interactions. The measured room-temperature conductivities of compounds 1 and 2 (7.0 × 10-5 and 2.0 × 10-5 S m-1, respectively) are indicative of semiconductor behavior which increases in the presence of photoillumination (3.5 × 10-4 and 4.9 × 10-4 S m-1, respectively). The measured I-V characteristics of compound 1 and 2 based thin film metal-semiconductor (MS) junction devices under irradiation and nonirradiation conditions show a nonlinear rectifying behavior, typical of a Schottky diode (SD). The rectification ratios (Ion/Ioff) of the SDs in the dark at ±2 V (26.96 and 31.96 for 1- and 2-based devices, respectively) increase to 44.19 and 79.42, respectively, upon light irradiation. The photoinduced behavior has been analyzed by thermionic emission theory, and to determine the diode parameters, the Cheung's method has been employed. These diode parameters indicate that compound 2 has a better performance in comparison to compound 1 and that these materials are good candidates for applications in electrochemical devices. Magnetic measurements show that both compounds present ferromagnetic Ni-Ni intrachain and weak antiferromagnetic interchain interactions. The isothermal magnetizations at 2 K show that both compounds are metamagnets with critical fields of ca. 130 mT in 1 and 90 mT in 2 at 2 K. In the ferromagnetic phase (above the critical field), both compounds exhibit a long-range ferromagnetic order with critical temperatures of around 3.5 K in 1 and 3.0 K in 2. DC and AC measurements with different applied DC fields confirm the metamagnetic behaviors and have allowed the determination of the magnetic phase diagram in both compounds.

Exploring aggregation-induced emission through tuning of ligand structure for picomolar detection of pyrene.

Tuning of ligand structures through controlled variation of ring number in fused-ring aromatic moiety appended to antipyrine allows detection of 7.8 × 10-12  M pyrene via aggregation-induced emission (AIE) associated with 101-fold fluorescence enhancement. In one case, antipyrine unit is replaced by pyridine to derive bis-methylanthracenyl picolyl amine. The structures of four molecules have been confirmed by single crystal X-ray diffraction analysis. Among them, pyrene-antipyrine conjugate (L) undergoes pyrene triggered inhibition of photo-induced electron transfer (PET) leading to water-assisted AIE.

Metal-Ligand Cooperative Approach To Achieve Dehydrogenative Functionalization of Alcohols to Quinolines and Quinazolin-4(3H)-ones under Mild Aerobic Conditions.

A simple metal-ligand cooperative approach for the dehydrogenative functionalization of alcohols to various substituted quinolines and quinazolin-4(3H)-ones under relatively mild reaction conditions (≤90 °C) is reported. Simple and easy-to-prepare air-stable Cu(II) complexes featuring redox-active azo-aromatic scaffolds, 2-arylazo-(1,10-phenanthroline) (L1,2), are used as catalyst. A wide variety of substituted quinolines and quinazolin-4(3H)-ones were synthesized in moderate to good isolated yields via dehydrogenative coupling reactions of various inexpensive and easily available starting materials under aerobic conditions. A few control experiments and deuterium labeling studies were carried out to understand the mechanism of the dehydrogenative coupling reactions, which indicate that both copper and the coordinated azo-aromatic ligand participate in a cooperative manner during the catalytic cycle.

Iron-Catalyzed/Mediated C-N Bond Formation: Competition between Substrate Amination and Ligand Amination.

Iron catalyzed carbon-nitrogen bond formation reactions of a wide variety of nucleophiles and aryl halides using well-defined iron-complexes featuring redox noninnocent 2-(arylazo)-1,10-phenanthroline (L1) ligands are reported. Besides substrate centered C-N coupling, C-N bond formation reactions were also observed at the ortho- and para-positions of the phenyl ring of the coordinated azo-aromatic scaffolds affording new tetradentate ligands, 2-N-aryl-(2-arylazo)-1,10-phenanthroline (L2), and tridentate ligands, 4 -N-aryl-(2-arylazo)-1,10-phenanthroline (L3), respectively. Control experiments and mechanistic studies reveal that the complex [FeL1Cl2] (1) undergoes in situ reduction during the catalytic reaction to produce the monoanionic complex [1]-, which then acts as the active catalyst. The metal (iron) and the coordinated ligand were found to work in a cooperative manner during the transfer processes involved in the fundamental steps of the catalytic cycle. Detailed experimental and theoretical (DFT) studies were performed to get insight into the competitive substrate versus ligand centered amination reactions.

Influence of foraminal enlargement on the healing of periapical lesions in rat molars.

OBJECTIVES: The aim of this study was to evaluate the influence of foraminal enlargement on the healing of induced apical periodontitis in a rat model. MATERIAL AND METHODS: Periapical lesions were bilaterally induced in mandibular first molars of 24 Wistar rats, through root canals exposure to the oral environment during 3 weeks. Endodontic treatment was performed in the mesial canal of right molars, which were separated into two experimental groups (n = 12/group). The foraminal enlargement group (FEG) received instrumentation in the entire root canal length, including the cemental canal, while in the non-foraminal enlargement group (NFEG), instrumentation was carried out 1 mm short of the apical foramen. Root canals were filled with gutta-percha and AH Plus sealer, in the same visit, 1 mm short of the apical foramen in both experimental groups. Left molars were not treated and served as a baseline control group. The animals were killed after 4 weeks, and their hemi-mandibles were prepared for radiographic and histological analysis. Data were analyzed by Student's t test and ANOVA. RESULTS: Only FEG presented lower areas of periapical radiolucency compared to the control (p < .05). Both FEG and NFEG allowed decreased inflammation intensity (p < .0001 and p < .01) and higher scores of cementum neoformation when compared to non-treated samples (p < .0001). FEG was more effective than NFEG in promoting biological seal, i.e., apical closure with cementum (p < .01). FEG, but not NFEG, showed lower scores of root resorption than the control. CONCLUSIONS: Foraminal enlargement during root canal preparation improved periapical healing in rat molars. CLINICAL SIGNIFICANCE: Foraminal enlargement has been suggested to improve disinfection at the apical portion of root canals. This procedure may favor the healing of chronic periapical lesions.

Correction to: Influence of foraminal enlargement on the healing of periapical lesions in rat molars.

Figures 2 and 3 in the published version of this article contained a mistake. CCP and DCP should have been FEG and NFEG. Correct figures are presented here.

New Molybdenum(II) Complexes with α-Diimine Ligands: Synthesis, Structure, and Catalytic Activity in Olefin Epoxidation.

Three new complexes [Mo(η³-C3H5)Br(CO)2{iPrN=C(R)C5H4N}], where R = H (IMP = N-isopropyl 2-iminomethylpyridine), Me, and Ph, were synthesized and characterized, and were fluxional in solution. The most interesting feature was the presence, in the crystal structure of the IMP derivative, of the two main isomers (allyl and carbonyls exo), namely the equatorial isomer with the Br trans to the allyl and the equatorial with the Br trans to one carbonyl, the position trans to the allyl being occupied by the imine nitrogen atom. For the R = Me complex, the less common axial isomer was observed in the crystal. These complexes were immobilized in MCM-41 (MCM), following functionalization of the diimine ligands with Si(OEt)3, in order to study the catalytic activity in olefin epoxidation of similar complexes as homogeneous and heterogeneous catalysts. FTIR, 13C- and 29Si-NMR, elemental analysis, and adsorption isotherms showed that the complexes were covalently bound to the MCM walls. The epoxidation activity was very good in both catalysts for the cis-cyclooctene and cis-hex-3-en-1-ol, but modest for the other substrates tested, and no relevant differences were found between the complexes and the Mo-containing materials as catalysts.

Redox-Induced Interconversion and Ligand-Centered Hemilability in NiII Complexes of Redox-Noninnocent Azo-Aromatic Pincers.

A series of nickel(II) complexes, namely, [NiII(La-c)2Cl2] (1a-c), [NiII(La,b)3](X)2 {([2a](X)2, [2b](X)2) (X = ClO4, I3)}, [NiII(Lc)2(OH2)2](ClO4)2 ([3](ClO4)2) and [NiII{(La,b)·-}2] (4a, 4b) featuring the redox-active tridentate azo-aromatic pincer ligand 2-(arylazo)-1,10-phenanthroline (L) were synthesized. The coordinated azo-aromatic ligand showed reversible hemilability depending on its formal oxidation state. On the one hand, in its native state, the unreduced ligand L shows bidentate coordination; the 1,10-phenanthroline moiety binds the central Ni(II) atom in a bidentate fashion, while the azo-chromophore remains pendent. On the other hand, the one-electron reduced ligand [L]·- binds the nickel(II) atom in a tridentate fashion. In complexes 1, [2]2+, and [3]2+, the 1,10-phenanthroline moiety of the neutral unreduced azo-aromatic ligand L binds the central nickel(II) atom in a bidentate fashion, while the azo-chromophore remains pendent. The complex 4 is a singlet diradical species, where two monoanionic azo-anion radical ligands [L]·- are bound to the central nickel(II) center in a tridentate fashion. Redox-induced reversible hemilability of the coordinated azo-aromatic ligand L was revealed from the interconversion of the synthesized complexes upon reduction and oxidation. Complex 1 upon reduction transformed to complex 4 with the loss of two chlorido ligands, whereas the complex 4 upon oxidation in the presence of excess chloride (LiCl) source transformed back to 1. Similarly, the complexes [2]2+ and 4 were also found to be interconvertible upon reduction and oxidation, respectively. Thorough experimental and density functional theory studies were performed to unveil the electronic structures of the synthesized complexes, and attempt was made to understand the redox-induced hemilability of the coordinated azo-aromatic ligand L.

Redox Noninnocent Azo-Aromatic Pincers and Their Iron Complexes. Isolation, Characterization, and Catalytic Alcohol Oxidation.

The new redox-noninnocent azoaromatic pincers 2-(arylazo)-1,10-phenanthroline (L1) and 2,9-bis(phenyldiazo)-1,10-phenanthroline (L2) are reported. The ligand L1 is a tridentate pincer having NNN donor atoms, whereas L2 is tetradentate having two azo-N donors and two N-donor atoms from the 1,10-phenanthroline moiety. Reaction of FeCl2 with L1 or L2 produced the pentacoordinated mixed-ligand Fe(II) complexes FeL1Cl2 (1) and FeL2Cl2 (2), respectively. Homoleptic octahedral Fe(II) complexes, mer-[Fe(L1)2](ClO4)2 [3](ClO4)2 and mer-[Fe(L2)2](ClO4)2 [4](ClO4)2, have been synthesized from the reaction of hydrated Fe(ClO4)2 and L1 or L2. The ligand L2, although having four donor sites available for coordination, binds the iron center in a tridentate fashion with one uncoordinated pendant azo function. Molecular and electronic structures of the isolated complexes have been scrutinized thoroughly by various spectroscopic techniques, single-crystal X-ray crystallography, and density functional theory. Beyond mere characterization, complexes 1 and 2 were successfully used as catalysts for the aerobic oxidation of primary and secondary benzylic alcohols. A wide variety of substituted benzyl alcohols were found to be converted to the corresponding carbonyl compounds in high yields, catalyzed by complex 1. Several control reactions were carried out to understand the mechanism of this alcohol oxidation reactions.

Deprotonation Induced Ligand Oxidation in a Ni(II) Complex of a Redox Noninnocent N(1)-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation.

Two nickel(II)-complexes, [Ni(II)(H3L)2](ClO4)2 ([1](ClO4)2) and [Ni(II)(HL)2] (2), containing the redox-active tridentate ligand N(1)-(2-aminophenyl)benzene-1,2-diamine (H3L) have been synthesized. Complex [1](ClO4)2 is octahedral containing two neutral H3L ligands in a facial coordination mode, whereas complex 2 is a singlet diradical species with approximately planar configuration at the tetracoordinate metal atom with two pendant NH2 side arms from each of the coordinated ligands. Both complexes are found to be chemically interconvertible; complex [1](2+) gets converted to complex 2 when exposed to base and oxygen via simultaneous deprotonation and oxidation of the coordinated ligands. Molecular and electronic structures of the isolated complexes are scrutinized thoroughly by various spectroscopic techniques, single crystal X-ray crystallography, and density functional theory. The observed dissociation of a ligand arm upon oxidation of the ligand was exploited to bring about catalytic alcohol oxidation using coordinatively saturated complex [1](ClO4)2 as a catalyst precursor. Both the complexes [1](ClO4)2and 2 were tested for catalytic oxidation of both primary and secondary alcohols.

Single crystal to single crystal (SC-to-SC) transformation from a nonporous to porous metal-organic framework and its application potential in gas adsorption and Suzuki coupling reaction through postmodification.

A new amino-functionalized strontium-carboxylate-based metal-organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC-to-SC) transformation upon desolvation. Both structures have been characterized by single-crystal X-ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent -NH2 groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine-2-carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross-coupling reaction. The compound shows high activity towards the C-C cross-coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m(2) g(-1). The material also possesses good CO2 (8 wt %) and H2 (1.87 wt %) adsorption capabilities.

Insight into ferromagnetic interactions in CuII-LnIII dimers with a compartmental ligand.

In the last two decades, efforts have been devoted to obtaining insight into the magnetic interactions between CuII and LnIII utilizing experimental and theoretical means. Experimentally, it has been observed that the exchange coupling (J) in CuII-LnIII systems is often found to be ferromagnetic for ≥4f7 metal ions. However, exchange interactions at sub-Kelvin temperatures between CuII and the anisotropic/isotropic LnIII ions are not often explored. In this report, we have synthesized a series of heterobimetallic [CuLn(HL)(µ-piv)(piv)2] complexes (LnIII = Gd (1), Tb (2), Dy (3) and Er (4)) from a new compartmental Schiff base ligand, N,N'-bis(3-methoxy-5-methylsalicylidene)-1,3-diamino-2-propanol (H3L). X-ray crystallographic analysis reveals that all four complexes are isostructural and isomorphous. Magnetic susceptibility measurements reveal a ferromagnetic coupling between the CuII ion and its respective LnIII ion for all the complexes, as often observed. Moreover, µ-SQUID studies, at sub-Kelvin temperatures, show S-shaped hysteresis loops indicating the presence of antiferromagnetic coupling in complexes 1-3. The antiferromagnetic interaction is explained by considering the shortest Cu⋯Cu distance in the crystal structure. The nearly closed loops for 1-3 highlight their fast relaxation characteristics, while the opened loops for 4 might arise from intermolecular ordering. CASSCF calculations allow the quantitative assessment of the interactions, which are further supported by BS-DFT calculations.

Logical model of reception and risk classification for women with pre-eclampsia and eclampsia.

OBJECTIVE: To describe the validation of the Logical Model of Reception and Risk Classification for women with pre-eclampsia/eclampsia in a high-risk maternity hospital. METHOD: Evaluative research with a quantitative approach. The elaboration and validation of the Logical Model were systematized in stages related to the scope review, preparation of the document guided by the Donabedian model and validation by 12 stakeholders, aiming at the assessment of the Content Validation Index. RESULTS: The problem that gave rise to the intervention was elaborated, supporting the construction of the Logical Model. Agreement was reached on 24 items, reaching a Content Validation Index of 0.99. Stakeholders included contributions regarding correlations between elements of the structure and process. CONCLUSION: The document achieved high content validity and could contribute to decision-making by managers in the Reception and Risk Classification sectors for women with pre-eclampsia and/or eclampsia.

Chemical fixation of atmospheric CO2 in tricopper(II)-carbonato complexes with tetradentate N-donor ligands: reactive intermediates, probable mechanisms, and catalytic and magneto-structural studies.

In the present era, the fixation of atmospheric CO2 is of significant importance and plays a crucial role in maintaining the balance of carbon and energy flow within ecosystems. Generally, CO2 fixation is carried out by autotrophic organisms; however, the scientific community has paid substantial attention to execute this process in laboratory. In this report, we synthesized two carbonato-bridged trinuclear copper(II) complexes, [Cu3(L1)3(µ3-CO3)](ClO4)3 (1) and [Cu3(L2)3(µ3-CO3)](ClO4)3 (2) via atmospheric fixation of CO2 starting with Cu(ClO4)2·6H2O and easily accessible pyridine/pyrazine-based N4 donor Schiff base ligands L1 and L2, respectively. Under very similar reaction conditions, the ligand framework embedded with the phenolate moiety (HL3) fails to do so because of the reduction of the Lewis acidity of the metal center, inhibiting the formation of a reactive hydroxide bound copper(II) species, which is required for the fixation of atmospheric CO2. X-ray crystal structures display that carbonate-oxygen atoms bridge three copper(II) centers in µ3syn-anti disposition in 1 and 2, whereas [Cu(HL3)(ClO4)] (3) is a mononuclear complex. Interestingly, we also isolated an important intermediate of atmospheric CO2 fixation and structurally characterized it as an anti-anti µ2 carbonato-bridged dinuclear copper(II) complex, [Cu2(L2)2(µ2-CO3)](ClO4)2·MeOH (2-I), providing an in-depth understanding of CO2 fixation in these systems. Variable temperature magnetic susceptibility measurement suggests ferromagnetic interactions between the metal centers in both 1 and 2, and the results have been further supported by DFT calculations. The catalytic efficiency of our synthesized complexes 1-3 was checked by means of catechol oxidase and phenoxazinone synthase-like activities. While complexes 1 and 2 showed oxidase-like activity for aerobic oxidation of o-aminophenol and 3,5-di-tert-butylcatechol, complex 3 was found to be feebly active. ESI mass spectrometry revealed that the oxidation reaction proceeds through the formation of complex-substrate intermediations and was further substantiated by DFT calculations. Moreover, active catalysts 1 and 2 were effectively utilized for the base-free oxidation of benzylic alcohols in the presence of air as a green and sustainable oxidant and catalytic amount of TEMPO in acetonitrile. Various substituted benzylic alcohols smoothly converted to their corresponding aldehydes under very mild conditions and ambient temperature. The present catalytic protocol showcases its environmental sustainability by producing minimal waste.

Phenolate-thiazole based reversible "turn-on" chemosensor for the selective detection of carbonate anion: X-ray crystallography, DFT/TDFT, and cell study.

A new phenolate-thiazole derivative (L) has been synthesized and structurally characterized.The chemo-sensing activity of L is detected by the naked eye for the aqueous carbonate anion in the pH range of 4 to 8. The selective 'turn-on' fluorescence occurs through the formation of a stable intermediate L∙CO32-(1) following the PET mechanism. The limit of detection (LOD) is found 0.18 µM based on the absorbance-based assay.The quinonoid form of bromophenol unit binds strongly with CO32- through thiazole nitrogen and hydrazinic nitrogen. Further, the selective holding of CO32- anion over other planar tetranuclear anions (e.g., SO32-, NO3-) happens with several intra and intermolecular hydrogen bonds as envisaged by the DFT/TDFT study. The formation mechanism of L∙CO32- is proposed based on experimental and theoretical studies. The biological experiments (MTT and cell imaging)reveal the non-cytotoxicity nature of L and the biocompatible uptake of L mostly in the cytoplasm at physiological pH.