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Four novel di-nuclear yttrium catalysts coordinated by bis(benzotriazole iminophenolate) (BiIBTP) ligands have been synthesized and structurally characterized. The one-pot procedure of BiIBTP pro-ligand with [Y(NO3)3.6H2O] (1.0 equiv.) and 2-nitrophenol derivative (1.0 equiv.) in the presence of triethylamine (5.0 equiv.) under refluxing MeOH solution gave bimetallic yttrium nitrophenolate complexes 1–4, [(μ-BiIBTP)Y(L)]2 (BiIBTP = C13CBiIBTP or C83CBiIBTP; L = 2-nitrophenolate or 2,4-dinitrophenolate) with good to high yields. The solid-state structure of 1 and 3–4 exhibits a di-yttrium(III) di-nitrophenolate species with the pentadentate BiIBTP ligand chelating two metal atoms. Versatile catalysis towards ring-opening polymerization of cyclic ester and copolymerization of internal epoxides with carbon dioxide (CO2) or phthalic anhydride (PA) catalyzed by these di-yttrium nitrophenolate complexes was systematically studied. Experimental results revealed that air-stable complexes 3 and 4 were shown to effectively catalyze not only lactide polymerization but also copolymerization of cyclohexene oxide (CHO) with CO2 or PA. Among these compounds, di-Y complex 4 was the most active catalyst for the ring-opening polymerization of l -lactide in combination with 9-anthracenemethanol, providing poly( l -lactide)s having the expected molecular weight and narrow molecular weight distribution. Furthermore, catalyst 3 was capable of copolymerizing CO2 and CHO in the presence of co-catalysts under mild conditions, producing perfectly alternating poly(cyclohexene carbonate)s with the controllable character. In addition, the molecular weight controllable poly(PA-co-CHO)s with high ester linkage contents could be afforded on copolymerizing PA and CHO utilizing di-yttrium complex 3 as the catalyst. This work provides the facilely synthesized di-nuclear yttrium complexes as versatile catalysts for three different types of polymerization catalysis.

A novel series of well-defined dicarboxylate dinuclear nickel complexes containing benzotriazole based 1,3-diamine-bisphenolate (1,3-DiBTP) ligands were readily synthesized through a one-pot procedure, which were highly active single-component catalysts for copolymerization of CO

A family of di-nuclear bis(benzotriazole iminophenolate) (BiIBTP) cobalt complexes containing diverse ancillary carboxylate derivatives have been synthesized and structurally characterized. The one-pot synthesis of the BiIBTP ligand precursor with cobalt perchlorate salt (2.0 equiv.) and carboxylic acid derivatives (2.0 or 5.0 equiv.) in the presence of triethylamine (5.0 equiv.) under refluxing methanolic solution generated bimetallic di-carboxylate Co(II)/Co(II) complexes [(C83CBiIBTP)Co2(O2CR)2] (R = C6H5 (1), C6F5 (2), 4-CF3–C6H4 (3), 4-OMe–C6H4 (4), CF3 (5)) in ≧65% yields. Interestingly, the Co(II)/Co(III) mixed-valence complex 6 resulted from the treatment of 1 with silver perchlorate (1.0 equiv.) as the oxidizing agent under an O2-atmosphere in 50% yield. The crystal structure of 6 reveals an ionic and di-nuclear benzoate species composed of a cationic moiety formulated as [(C83CBiIBTP)Co2(O2CC6H5)2]+ and a counterbalanced perchlorate anion, and both metal atoms are attributed to hexa-coordinated cobalt ions with varied coordination environments. Catalysis results of CO2/epoxide copolymerization indicated that complex 1 was more efficient than 2–6 where compound 6 was shown to be the least active. Co complex 1 incorporating benzoate coligands was demonstrated to effectively catalyze the CO2-copolymerization of cyclohexene oxide (CHO), 4-vinyl-1,2-cyclohexene oxide or cyclopentene oxide, producing the associated CO2-based polycarbonates with >99% carbonate repeated units under optimal conditions. Not only the controllable character of complex 1 for CO2/CHO copolymerization is enabled, but also 1 has been shown to catalyze such a copolymerization in the “immortal” manner. Using the same di-cobalt catalyst in combination with excess ratios of neopentyl glycol (up to 150 equiv.) as the chain transfer agent could give low molecular weight poly(cyclohexene carbonate) polyols with monomodal molecular weight distributions. This work offers the facilely prepared di-nuclear cobalt complexes as catalysts for the efficient catalysis of CO2-copolymerization.

A series of di-nuclear metal acetate complexes 1–6 incorporated by nitrogen heterocycle-containing salen-type ligands have been synthesized, structurally characterized and performed as catalysts to prepare biodegradable polycarbonates and polyesters. Their catalytic performances for copolymerization of carbon dioxide-epoxides or cyclic anhydride-epoxides were systematically examined. Bimetallic nickel(II) complexes 1, 2 and 5 were active catalysts for the alternating copolymerization of cyclohexene oxide (CHO) with CO2; di-nickel complex 1 was shown to be the most effective and selective, leading to obtaining poly(cyclohexene carbonate)s with the best efficiency among them. Moreover, complex 1 was also found to be versatile for the ring-opening copolymerization of CO2 with different cyclic epoxides to give the corresponding polycarbonates. Additionally, di-cobalt(II) analogs 3, 4 and 6 were efficient catalysts for the alternating copolymerization of CHO and phthalic anhydride (PA) under mild conditions. Based on the results of catalytic studies, complex 3 was demonstrated to be the most active one CHO-PA copolymerization, producing the polymeric products with a “controlled” manner involving controllable molecular weights and narrow polydispersity. Interestingly, Co complex 3 was also able to catalyze the copolymerization of PA with 4-vinyl-1,2-cyclohexene oxide to obtain the associated polyester with the vinyl functionality on the side chains, which was further functionalized with tertiary amine moieties via thiol-ene click functionalization and converted to nanofibers through electrospinning. Due to the incorporation of polar groups, the resulting tertiary amine-modified polyester nanofibers that exhibit an improved hydrophilic property relative to their un-modified counterpart have been considered to have high potential to be utilized as a new functional fiber material.

Four new 2D indium metal-organic frameworks (MOFs) (Me2NH2)[In(SBA)2] (1), (Me2NH2)[In(SBA)(BDC)] (2), (Me2NH2)[In(SBA)(BDC-NH2)] (3), and (NH4)3[In3Cl2(BPDC)5] (4), (H2SBA = 4,4'-sulfonyldibenzoic acid; H2BDC = 1,4-benzenedicarboxylic acid; H2BDC-NH2 = 2-amino-1,4-benzenedicarboxylic acid; H2BPDC = 4,4'-biphenyldicarboxylic acid) have been synthesized under solvothermal reaction conditions for compounds 1 to 3 and the DES (deep eutectic solvent) reaction has been attempted for compound 4. The structure of these MOFs has been determined by using single crystal X-ray diffraction study and all of theses four 2D monolayer framework with porous properties. The N2 gas sorption measurements indicated that Brunauer-Emmer-Teller (BET) and Langmuir surface areas of compound 1 are 207 and 301 m2 g-1, respectively, which is probably the first one having substantial gas uptake properties in the entire 2D In-MOF family to date. Furthermore, these new indium MOFs on the addition of n-Bu4NBr were active for the cycloaddition of CO2 and propylene oxide, generating propylene carbonates in high conversions under mild conditions. Particularly, the most active MOF 4 was found to efficiently couple CO2 with a series of terminal epoxides to give the corresponding cyclic organic carbonates with high selectivities.

This study reports that a series of structurally well-defined mono- and di-nuclear cobalt complexes containing the amine-bis(benzotriazole phenolate) ligand (amine-BiBTP) have been synthesized and fully characterized. The one-pot reaction of the amine-BiBTP ligand precursor with cobalt nitrate salt in the presence of triethylamine under refluxing methanolic solution generated di-nuclear cobalt(II) complexes [(C1NNBiBTP)2Co2] (1). The mono-Co(II) complex [(C1NNBiBTP)CoR] (R = DMAP (2), tBuPy (3)) could be prepared by 1 with a stoichiometric amount of 4-(dimethylamino)pyridine (DMAP) or 4-tert-butylpyridine (tBuPy) to yield a five-coordinated mononuclear cobalt species. Interestingly, the Co(III) complexes 4–7 resulted from the treatment of 2 or 3 with silver nitrate/trifluoroacetate as the oxidizing agent, and an ionic and mononuclear species formulated as [(C1NNBiBTP)CoR2]X (R = DMAP, X = NO3 (4), R = DMAP, X = CF3COO (5), R = tBuPy, X = NO3 (6), R = tBuPy, X = CF3COO (7)) could be formed. Versatile catalysis towards copolymerization of internal epoxides with anhydride catalyzed by these Co(II)/Co(III) was systematically studied under mild conditions. Experimental results revealed that complex 4 was shown to effectively catalyze copolymerization of cyclohexene oxide (CHO) with phthalic anhydride (PA), resulting in copolymers with a high alternating microstructure possessing ≥ 99% ester-linkage contents.

A unique cluster of lithium isopropoxide assisted tantalum isopropoxide derivative incorporating bidentate ketiminate ligand is reported and structurally characterized. Reaction between Li(OCMeCHCMeNAr) and TaCl5 in toluene at room temperature generates compound 1, (OCMeCHCMeNAr)TaCl4, in relatively high yield. Further reacting of 1 with excess amount of LiiOPr in diethylether affords the tantalum-lithium bimetallic cluster {[Li(OCMeCHCMeNAr)]Ta(OiPr)5(LiOiPr)(LiCl)}2 (2). The molecular geometry of 2 reveals as an edge-sharing bis(open-cube) that it consists two Li-Cl edge-sharing bis(open-cube)TaLi3O5Cl units in its core structure.

This study reports a two-step method to synthesize spermidine-capped fluorescent carbon quantum dots (Spd-CQDs) and their potential application as an antibacterial agent. Fluorescent carbon quantum dots (CQDs) are synthesized by pyrolysis of ammonium citrate in the solid state and then modified with spermidine by a simple heating treatment without a coupling agent. Spermidine, a naturally occurring polyamine, binds with DNA, lipids, and proteins involved in many important processes within organisms such as DNA stability, and cell growth, proliferation, and death. The antimicrobial activity of the as-synthesized Spd-CQDs (size ≈4.6 nm) has been tested against non-multidrug-resistant E. coli, S. aureus, B. subtilis, and P. aeruginosa bacteria and also multidrug-resistant bacteria, methicillin-resistant S. aureus (MRSA). The minimal inhibitory concentration value of Spd-CQDs is much lower (>25 000-fold) than that of spermidine, indicating their promising antibacterial characteristics. The mechanism of antibacterial activity is investigated, and the results indicate that Spd-CQDs cause significant damage to the bacterial membrane. In vitro cytotoxicity and hemolysis analyses reveal the high biocompatibility of Spd-CQDs. To demonstrate its practical application, in vitro MRSA-infected wound healing studies in rats have been conducted, which show faster healing, better epithelialization, and formation of collagen fibers when Spd-CQDs are used as a dressing material.

The synthesis of structurally well-characterized dinuclear nickel complexes bearing a new type of pyrazolyl based diamine-bisphenolate ligand was reported for the first time. Catalysis towards nickel-catalyzed copolymerization of CO2 with cyclohexene oxide (CHO) by these newly prepared bimetallic complexes was systematically investigated. Particularly, dinickel complex 4 supporting 2-nitrophenoxide coligands was demonstrated to effectively catalyze CO2-copolymerization of CHO, 4-vinyl-1,2-cyclohexene oxide or cyclopentene oxide, generating the corresponding CO2-based polycarbonates with >99% carbonate linkages under optimal conditions. Kinetic studies of CO2/CHO copolymerization revealed that such copolymerization catalysis is first-order in dinickel complex 4 and second-order in CHO concentration.

We report the synthesis of structurally well-characterized di-nuclear nickel bis(benzotriazole iminophenolate) (BiIBTP) complexes containing diverse mono- or bi-dentate monoanionic coligands for the utilization of copolymerization of carbon dioxide (CO2) with internal epoxides. The molecular structures of complexes 1–3 can be ascribed to bimetallic nickel(II) species containing a hexadentate BiIBTP main ligand and two homo-coligands of pentafluorobenzoate, pentafluorophenolate or chloride, whereas 4 and 5 are BiIBTP-ligated di-nickel chloride analogues mixed with carboxylate coligands. Di-nickel complexes 1 and 3 supported by O2CC6F5 and Cl coligands were demonstrated to be efficient catalysts for alternating copolymerization of CO2 with cyclohexene oxide (CHO) to afford CO2-based poly(cyclohexene carbonate)s (PCHCs) with >99% carbonate repeated units. Particularly, di-Ni di-chloride complex 3 was capable of giving high activity with a turnover frequency of 688 h−1 for such copolymerization under the optimal conditions. Interestingly, di-Ni catalyst 1 enables us to produce the low molecular weight di-hydroxyl end-capped PCHCs with unimodal molecular weight distributions while commercially available CHO without further purification was used as the epoxide monomer. In addition to CO2-CHO copolymerization, bimetallic complex 1 was also found to effectively copolymerize CO2 with cyclopentene oxide, generating highly alternating poly(cyclopentene carbonate)s with molecular weights in a broad range. Kinetic studies of CO2/CHO copolymerization catalyzed by 1 were investigated using 1H NMR spectroscopy and revealed the first-order dependence for both catalyst 1 and CHO concentrations.