A new bis-β-diketone ligand, 3,5-bis-(3-oxobutanoyl)benzoic acid (BOBA), has been designed and prepared for the self-assembly of the dinuclear triple-helical Fe(III) complex Fe2(BOBA)3 and the mononuclear Cd(II) complex Cd(BOBA)2(py)3. The ligand BOBA was proved to exist in the enol form both in the solid-state and in solution by single crystal X-ray analysis and 1H and 13C NMR studies. X-ray crystallographic analysis reveals that dinuclear Fe(III) complexes consist of a triple helicate, within which the Fe(III) ions are in pseudo-octahedral environments, bound to three diketonate units from three different ligands, while Cd(BOBA)2(py)3 features a mononuclear motif with the Cd(II) center taking a distorted pentagonal pyramidal geometry that is filled by two carboxylates from two BOBA ligands and three pyridines. The photophysical properties of the ligand and the two complexes are thoroughly investigated. Compared with the free ligand BOBA and Cd(BOBA)2(py)3, the helicate Fe2(BOBA)3 displays much stronger fluorescence upon excitation at 289 nm, representing a rare case of a luminescent transition metal coordination compound without a d10 configuration. Time-dependent density functional theory (TD-DFT) calculations indicate that transformation from an n–π* to a π–π* character is responsible for the fluorescence enhancement observed for Fe2(BOBA)3.
Abstract The natural DNA double helix consists of two strands of nucleotides that are held together by multiple hydrogen bonds. Here we propose to build an artificial double helix from fragments of two strands connected by covalent linkages therein, but with halogen bonding as the driving force for self-assembling the fragments to the double helix. We succeed in building such a double helix in both solution and solid state, by using a bilateral N -( p -iodobenzoyl)alanine based amidothiourea which in its folded cis -form allows double and crossed C−I···S halogen bonds that lead to right- or left-handed double helix when the two alanine residues are of the same L,L- or D,D-configuration. The double helix forms in dilute CH 3 CN solution of the micromolar concentration level, e.g., 5.6 μM from 2D NOESY experiments and exhibits a high thermal stability in solution up to 75 °C, suggesting cooperative and thereby strong intermolecular double crossed halogen bonding that makes the double helix stable. This is supported by the observed homochiral self-sorting in solution.
Abstract Background During the biomass-to-bio-oil conversion process, many studies focus on studying the association between biomass and bio-products using near-infrared spectra (NIR) and chemical analysis methods. However, the characterization of biomass pyrolysis behaviors using thermogravimetric analysis (TGA) with support vector machine (SVM) algorithm has not been reported. In this study, tobacco was chosen as the object for biomass, because the cigarette smoke (including water, tar, and gases) released by tobacco pyrolysis reactions decides the sensory quality, which is similar to biomass as a renewable resource through the pyrolysis process. Results SVM algorithm has been employed to automatically classify the planting area and growing position of tobacco leaves using thermogravimetric analysis data as the information source for the first time. Eighty-eight single-grade tobacco samples belonging to four grades and eight categories were split into the training, validation, and blind testing sets. Our model showed excellent performances in both the training and validation set as well as in the blind test, with accuracy over 91.67%. Throughout the whole dataset of 88 samples, our model not only provides precise results on the planting area of tobacco leave, but also accurately distinguishes the major grades among the upper, lower, and middle positions. The error only occurs in the classification of subgrades of the middle position. Conclusions From the case study of tobacco, our results validated the feasibility of using TGA with SVM algorithm as an objective and fast method for auto-classification of tobacco planting area and growing position. In view of the high similarity between tobacco and other biomasses in the compositions and pyrolysis behaviors, this new protocol, which couples the TGA data with SVM algorithm, can potentially be extrapolated to the auto-classification of other biomass types.
Marvelous natures of alkali and alkaline earth metal hydrides in catalyzing chemical transformations are being discovered. However, the synthesis of (sub)nanostructured metal hydrides, critically important to enhance their catalytic performances, is yet a very challenging task. Herein, we develop a highly reactive heterogeneous catalyst comprising atomically dispersed barium hydrides on MgO support with an ultrahigh barium loading of up to 20 wt% via a convenient preparation method involving liquid-ammonia impregnation followed by hydrogenation. The surface barium hydride species not only exhibits extraordinary reactivity toward H2 activation at room temperature, but also enables the highly efficient hydrogen isotope exchange (HIE) of both sp3 C–H and sp2 C–H bonds in nonactivated alkylarenes using D2 as the deuterium source under mild conditions. The deuteration rate at benzylic site is two orders of magnitude higher than that of bulk BaH2. This study offers an alternative synthetic route for the manufacture of deuterium-labeled compounds using a heterogenous transition metal-free hydride catalyst beyond the widely studied molecular metal complexe catalysts. Hydrogen isotope exchange is essential for the synthesis of deuterium-labeled compounds but remains challenging under mild conditions. This study demonstrates the selective deuteration of alkylarenes at room temperature using atomically dispersed surface barium hydride.
Bacterial membrane vesicles (BMVs) are crucial biological vehicles for facilitating interspecies and interkingdom interactions. However, the extent and mechanisms of BMV involvement in bacterial-algal communication remain elusive. This study provides evidence of BMVs delivering cargos to targeted microalgae. Membrane vesicles (MVs) from Chitinimonas prasina LY03 demonstrated an algicidal profile similar to strain LY03. Further investigation revealed Tambjamine LY2, an effective algicidal compound, selectively packaged into LY03-MVs. Microscopic imaging demonstrated efficient delivery of Tambjamine LY2 to microalgae Heterosigma akashiwo and Thalassiosira pseudonana through membrane fusion. In addition, the study demonstrated the versatile cargo delivery capabilities of BMVs to algae, including the transfer of MV-carried nucleic acids into algal cells and the revival of growth in iron-depleted microalgae by MVs. Collectively, our findings reveal a previously unknown mechanism by which algicidal bacteria store hydrophobic algicidal compounds in MVs to trigger target microalgae death and highlight BMV potency in understanding and engineering bacterial-algae cross-talk.
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