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Data-driven materials research can be used as an effective tool to supplement conventional approaches in designing new materials. Hollow glass microsphere (HGM) composites are widely used for high-temperature thermal insulation applications, and their synthesis is traditionally done by varying parameters of the constituents on a trial-and-error basis. In this work, a prediction tool based on a supervised machine learning (ML) model is developed to predict the effective thermal conductivity (ETC) of an HGM composite by tailoring the composition and parameters of the constituents to reduce the time and cost involved. A comprehensive database containing the various input features is generated from previous experimental investigations conducted on various HGM composites. ML models, namely random forest regression (RF), K-nearest neighbor (KNN), support vector regression (SVR), and artificial neural network (ANN), are used to predict the ETC of HGM composites. Feature importance analysis showed that the matrix material’s thermal conductivity and the composite’s bulk density have the highest impact on the ETC of the HGM composite, followed by porosity and average microsphere size. ANN emerged as the best model to predict HGM composite ETC with the lowest root mean square error and highest R2value for predictions. Moreover, a systematic approach for key feature selection using ANN shows that adding or omitting additional features beyond an optimal combination degrades the model’s predictive accuracy.

The present research aims to exploit the antioxidant and antibacterial activities of freshwater microalgae, Scenedesmus obliquus, by performing polarity-wise successive solvent extraction by hexane, chloroform, ethyl acetate, acetone, methanol, and water. The antibacterial and antioxidant activities of these crude extracts were evaluated, and a correlation was established between these two parameters. The methanol and water extracts showed the highest phenolic (18–23 mg GAE/g EW) and flavonoid (5–8 mg QE/g EW) contents, resulting in a maximum antioxidant activity (IC50= 61–76 μg/mL for DPPH and 60–75 μg/mL for ABTS), but a lower antibacterial activity (MIC = 250–1000 μg/mL). In contrast, the hexane and chloroform extracts showed lower content of phenolics (0.3–0.8 mg GAE/g EW), resulting in a very low antioxidant activity (IC50= 223–278 μg/mL for DPPH and 172–220 μg/mL for ABTS). The hexane and chloroform extracts contained both saturated and polyunsaturated fatty acids with carotenoids (4–6.2 mg/g DE) and lipids as their main constituents. Flavonoids like myricetin (0.3–0.56 μg/mg) and rutin (0.24–0.75 μg/mg) were identified and extracted from this algal strain for the first time. The hexane and chloroform extracts were effective on both Gram-positive and Gram-negative bacteria, exhibiting the highest antibacterial activity (MIC = 15.6–125 μg/mL). Overall, the polar solvent extracts of S. obliquuswere found to contain a high amount of phenolics and flavonoids than most reported microalgae species, making it a potential strain for developing industrially relevant biopharmaceuticals.

A water-soluble hexadentate ligand H4bedik was reproduced and employed to synthesize the corresponding mononegative [FeIIIbedik]−complex core. In the complex formation process, NaOH, KOH, and Ca(OH)2bases were used in order to have the corresponding cations as the counterpart of the mononegative complex core. Thus, formed complexes were designated as complex 1·H2O, Na+ion as the countercation; complex 2, K+ion as the countercation; and complex 3·H2O, 1/2 Ca2+ion as the countercation. Complexes were characterized by IR and mass spectrometric techniques. Additionally, the complexes were structurally characterized by single crystal X-ray diffraction analysis. In complex 1·H2O, where the Na+ion was present as a countercation, a two-dimensional (2D) zigzag layer structure was formed along the bcplane. The two adjacent layers were parallel to each other and propagated along the same direction, and the adjacent layers were connected to each other by H-bonding. Thus, a three-dimensional (3D) network was found. A K+ion-containing complex 2formed a one-dimensional (1D) linear network that propagated along the baxis. H-bonding driven 3D layers were also found in complex 2. Akin to complex 1·H2O, complex 3·H2O also formed a 2D layers structure; however, the structure was planar and not zigzag as observed in complex 1·H2O. In complex 3·H2O, two adjacent parallel layers were propagated along two opposite directions. Thermogravimetric analyses indicated that the stability of the complexes and the [FeIIIbedik]−complex core depended on the nature of the countercation. Longitudinal (r1) and transverse relaxivity (r2) measurements of aqueous solutions of the complexes have been performed. The value was cation-dependent and thus emphasized different interactions between [FeIIIbedik]−units in the presence of different cations.

The noninnocent ligand H2LAP(Ph)contained a bulky phenyl substituent at the orthoposition to the aniline moiety. The ligand reacted with 0.5 equiv of CuCl2·2H2O in the presence of Et3N under air and provided the corresponding Cu(II)-bis(imonosemiquinone) complex (1). The complex upon oxidation by a stoichiometric amount of ferrocenium hexafluorophosphate (FcPF6) yielded the four-coordinate [Cu(II)-(imonosemiquinone)(iminoquinone)]PF6complex (3), while the oxidation by an equivalent amount of CuCl2·2H2O produced the five-coordinate Cu(I)-bis(iminoquinone)Cl complex (2). Thus, a ligand-based oxidation followed by ligand-to-metal electron-transfer was realized for the latter oxidation process. Removal of the Cl–ion from complex 2rendered the four-coordinate complex 4. The oxidation state of both Cu(I) and iminoquinone moieties remained unaltered upon the change in the coordination number. All the complexes were characterized by X-ray crystallography. Complexes 2, 3, and 4were diamagnetic with an St= 0 ground state as evident by electron paramagnetic resonance (EPR) and 1H NMR measurements. The UV–vis–NIR spectra of all the complexes were dominated by charge-transfer transitions. Two oxidations and two reductions waves were noticed in the cyclic voltammogram (CV) of complex 1. Complex 2and complex 3underwent one oxidation and three reductions. Unlike complex 3, which experienced ligand-based oxidation, in complex 2the oxidation was metal-centered [oxidation of Cu(I)-to-Cu(II)]. UV–vis–NIR spectral changes during the fixed-potential coulometric one-electron oxidation and thereafter EPR analysis consolidated the metal-based oxidation in complex 2. Complex 2was air stable; however, it oxidized KO2to oxygen molecule, and complex 1was formed in due course as evident by UV–vis–NIR spectral changes and EPR measurements. Time dependent density functional theory calculations have been incorporated to assign the transitions that appeared in the UV–vis–NIR spectra of the complexes.

In non-isothermal flows, heatlines are used to depict the energy flow from hot surface to cold surface and help in visualizing the strength of the convective heat transfer as compared to the conductive heat transfer. Traditionally, researchers have plotted heatlines by solving heat-function equation in their solvers during the runtime. However, this requires access to the solver code and is time-consuming to implement. Further, the literature available so far only concerns simple geometric shapes. This work aims to document out-of-the-box methods for the visualization of heatlines which can be done as a post-processing exercise. A comparison of streamlines and heatlines, is at first presented to enhance the understanding of the application of heatlines in heat transfer problems and use the same technique in post-processing computer programs for visualizing heatlines. The procedures to plot heatlines using commercial (tecplot and cfd-post) and open-source (paraview) tools are presented. Illustrative examples of different computational geometries from past literature are validated to establish the efficacy of the method. Further, the method can be also applied to plot heatlines for complex geometries which is not feasible with the traditional approaches.

Disclosed here are a piperazine, a pyridine, and two carboxylate groups containing pentadentate ligand H2pmpa and its corresponding water-soluble Mn(II) complex (1). DFT-based structural optimization implied that the complex had pentagonal bipyramidal geometry where the axial positions were occupied by two water molecules, and the equatorial plane was constituted by the ligand ON3O donor set. Thus, a bis(aquated) disc-like Mn(II) complex has been synthesized. The complex showed higher stability compared with Mn(II)–EDTA complex [logKMnL= 14.29(3)] and showed a very high r1relaxivity value of 5.88 mM–1s–1at 1.41 T, 25 °C, and pH = 7.4. The relaxivity value remained almost unaffected by the pH of the medium in the range of 6–10. Although the presence of 200 equiv of fluoride and bicarbonate anions did not affect the relaxivity value appreciably, an increase in the value was noticed in the presence of phosphate anion due to slow tumbling of the complex. Cell viability measurements, as well as phantom MR images using clinical MRI imager, consolidated the possible candidature of complex 1as a positive contrast agent.

Single-molecule magnets (SMMs) retain a magnetization without applied magnetic field for a decent time due to an energy barrier Ufor spin-reversal. Despite the success to increase U, the difficult to control magnetic quantum tunneling often leads to a decreased effective barrier Ueffand a fast relaxation. Here, we demonstrate the influence of the exchange coupling on the tunneling probability in two heptanuclear SMMs hosting the same spin-system with the same high spin ground state St= 21/2. A chirality-induced symmetry reduction leads to a switch of the MnIII–MnIIIexchange from antiferromagnetic in the achiral SMM [MnIII6CrIII]3+to ferromagnetic in the new chiral SMM RR[MnIII6CrIII]3+. Multispin Hamiltonian analysis by full-matrix diagonalization demonstrates that the ferromagnetic interactions in RR[MnIII6CrIII]3+enforce a well-defined St= 21/2 ground state with substantially less mixing of MSsubstates in contrast to [MnIII6CrIII]3+and no tunneling pathways below the top of the energy barrier. This is experimentally verified as Ueffis smaller than the calculated energy barrier Uin [MnIII6CrIII]3+due to tunneling pathways, whereas Ueffequals Uin RR[MnIII6CrIII]3+demonstrating the absence of quantum tunneling.

Ligand H4Sar(AP/AP)contained two terminal amidophenolate units that were connected by a disulfane bridge. The ligand reacted with VOSO4·5H2O in the presence of Et3N under air and provided a mononuclear octahedral oxidovanadium complex (1). X-ray crystal structure analysis of complex 1revealed that the oxidation state of the V ion was V and the VO3+unit was coordinated to an iminosemiquinone radical anion. An isotopic signal at g= 1.998 in the X-band electron paramagnetic resonance (EPR) spectrum and the solution magnetic moment μeff= 1.98 μBat 298 K also supported the composition. The formation of complex 1preceded through the initial generation of a diamagnetic VO2+–iminoisemiquinone species, as established by time-dependent UV–vis–near-IR (NIR), X-band EPR, and density functional theory studies. The UV–vis–NIR spectrum of complex 1consisted of four ligand-to-metal charge-transfer transitions in the visible region, while an intervalence ligand-to-ligand charge transfer appeared at 1162 nm. The cyclic voltammogram of the complex showed four oxidation waves and one reduction wave. Spectroelectrochemical studies at fixed potentials revealed that the oxidation and reduction processes were ligand-based.

2-Aminophenol appended pentadentate ligand H2GanAPwas synthesized by mixing equimolar amounts of 2-[bis(2-pyridylmethyl)aminomethyl]aniline (A) and 3,5-di-tert-butyl catechol in hexane in the presence of Et3N under air. The ligand reacted with Fe(ClO4)2·6H2O or Fe(ClO4)3·6H2O in the presence of tetrabutylammonium perchlorate, and Et3N under air and provided a μ2oxo-bridged dinuclear iron complex (1). X-ray single-crystal analysis of complex 1revealed the presence of a furan derivative, resulting from the oxidative aromatic C–C bond cleavage product of 2-aminophenol derivative, in the coordination sphere of each iron center. Mechanistic investigation for the formation of complex 1established that in the absence of molecular oxygen no oxidation of the appended 2-amidophenolate unit took place. An iron(III)–amidophenolate complex, formed initially, further reacted with molecular oxygen and caused oxidative aromatic C–C bond cleavage via a putative alkylperoxo species.

The kinetics of chiral scandium(III)‐catalyzed hydroxymethylation of silicon enolates using aqueous formaldehyde have been investigated, and a reaction mechanism of this process in organic/aqueous medium is proposed.

The chiral triplesalen ligand H6chand provides three chiral salen ligand compartments in a meta‐phenylene arrangement by a phloroglucinol backbone. The two diastereomeric versions H6chandRRand H6chandrachave been used to synthesize the enantiomerically pure chiral complex [(FeCl)3(chandRR)] (3RR) and the racemic complex [(FeCl)3(chandrac)] (3rac). The molecular structure of the free ligand H6chandracexhibits at the terminal donor sides the O‐protonated phenol–imine tautomer and at the central donor sides the N‐protonated keto–enamine tautomer. The trinuclear complexes are comprised of five‐coordinate square‐pyramidal FeIIIions with a chloride at the axial positions. The crystal structure of 3racexhibits collinear chiral channels of ∼11 Å in diameter making up 33.6 % of the volume of the crystals, whereas the crystal structure of 3RRexhibits voids of 560 Å3. Mössbauer spectroscopy demonstrates the presence of FeIIIhigh‐spin ions. UV/Vis spectroscopy is in accordance with a large delocalized system in the central backbone evidenced by strong low‐energy shifts of the imine π–π* transitions relative to that of the terminal units. Magnetic measurements reveal weak intramolecular exchange interactions but strong magnetic anisotropies of the FeIIIions. Complexes 3racand 3RRare good catalysts for the sulfoxidation of sulfides providing very good yields and high selectivities with 3RRbeing enantioselective. A comparison of 3RRand [FeCl(salen′)] provides higher yields and selectivities but lower enantiomeric excess values (eevalues) for 3RRrelative to [FeCl(salen′)]. The low eevalues of 3RRappeared to be connected to a strong ligand folding in 3RR, opening access to the catalytically active high‐valent Fe–O species. The higher selectivity is assigned to a cooperative stabilization of the catalytically active high‐valent Fe–O species through the phloroglucinol backbone in the trinuclear complexes.

Reaction of MnCl2with a non-innocent ligand H3L results in an unprecedented mixed-valence trinuclear complex [MnIIMnIIIMnIV(L)(L)2(LIQ)Cl] whose structural and magnetic properties are described.

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