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Abstract: A novel calcium complex, [(DAIP)2Ca]2 (where DAIP-H=2-[(2-dimethylamino-ethylimino)methyl]phenol), is prepared in a one flask reaction by condensation of Ca(OMe)2 with DAIP-H in toluene/THF. Experimental results show that in the presence of various alcohols, [(DAIP)2Ca]2 efficiently initiates the ring-opening polymerization of l-lactide in a controlled fashion, yielding polymers with expectative molecular weight and low polydispersity indexes. Furthermore, kinetic studies show a first-order dependency on both [LA] and [BnOH]. [Copyright &y& Elsevier]

Abstract: Palladium-catalyzed Suzuki cross-coupling reactions employing Schiff-bases as ligands toward a series of substituted arylbromides and boronic acids were pursued. In the presence of a N,O-bidentate ligand, 2-[1-(2,4,6-trimethyl-phenylimino)-ethyl]-phenol 5 , the catalytic reactions could be carried out efficiently at room temperature with a wide array of arylbromides, even with electronically deactivated arenes. A deprotonated 5 , 5′, chelated palladium acetate complex, [ 5′Pd(II)(OAc)(solv)] 8 , was proposed as a precursor of a genuine catalytically active species. [Copyright &y& Elsevier]

Abstract: Two pentanuclear copper(I) thiolato clusters of the formula [Cu5(L)3]− (L = pyridine-2,6-dimethanethiolate (L1), (1); 4-methylpyridine-2,6-dimethanethiolate (L2), (2)) were synthesized utilizing a single-step procedure, and their structures were characterized by X-ray crystallography. The aforementioned pentanuclear complexes possess an interesting propeller-like Cu5S6 core where all Cu centers are three-coordinate. Electrospray ionization mass spectrometry (ESI-MS) investigation of the pentanuclear copper(I) thiolato clusters with added hetero-ligands demonstrated interesting ligand exchange behavior. The product distribution resulting from ligand exchange not only depended on the quantity of added ligand, but also was sensitive to the coordination ability of the ligand. The ESI-MS method used in this study can serve as a useful tool for probing exchange behavior in coordination metal complexes that cannot otherwise be determined by NMR. [Copyright &y& Elsevier]

Self-assembled PCL–SS-PMAA micelles to co-deliver PTX and CDDP for combination chemotherapy. • A redox-responsive PCL-SS-PMAA micelle was fabricated to improve reduction response for DDS. • PTX and CDDP were efficiently released from the micelle under an acid condition with a reducing agent. • Encapsulating the dual drugs into the micelle exerted superior antitumor activity over other combinations. Combining dual drugs in one vehicle to cancer cells offers spatiotemporal localization of drug at the site of action, leading to synergistic therapeutic effects and reduced side effects. To improve pH/redox responsiveness to the tumor microenvironments for cancer therapy, a pH/redox-responsive micelle based on poly(ε-caprolactone)-SS-poly(methacrylic acid) (PCL-SS-PMAA) diblock copolymer was fabricated for dual drug delivery. The PCL-SS-PMAA was formulated into a core-shell micelle (PSPm) in an aqueous solution. The critical micelle concentration (CMC) values of PSPm were 7.94 × 10−3 mg mL-1 at pH 5.0 and 1.00 × 10-2 mg mL-1 at pH 7.4. The hydrodynamic diameters of PSPm were within 210–270 nm, depending on pH values. Changes in morphology and size of PSPm were clearly observed before and after exposure to a reducing agent. Paclitaxel (PTX) was encapsulated into the core and cisplatin (CDDP) was chelated on the shell of PSPm, with both PTX and CDDP being efficiently released from PSPm in the presence of a reducing agent in an acid condition. MTT and annexin V/propidium iodide dual staining results demonstrated that co-loading of CDDP and PTX into PSPm had a synergistic effect in killing lung cancer cells and exerted superior antitumor activity over the combination of single drug-loaded PSPm or the combination of free-CDDP and free-PTX at equivalent drug amounts. Hence, encapsulating the dual drugs into PSPm exhibits a synergistic effect for potential lung cancer therapy. [ABSTRACT FROM AUTHOR]

• AMM associated Al complexes had higher activity than that of ketiminate ligands. • Steric hindrance groups in the ligands revealed the greater catalytic activity. • Electron-withdrawing groups in the ligands revealed the greater catalytic activity. • Ligands with chelating group reduced the reactivity of ring-opening polymerization. A series of Al complexes bearing diethyl 2-((arylamino)methylene)malonate and diethyl 2-((alkylamino)methylene)malonate ligands (AMM ligands) were synthesized and their application in the ring-opening polymerization of ε -caprolactone was studied. All the Al complexes bearing AMM ligands exhibited higher catalytic activity (approximately 2.8–16.5 fold) than those Al complexes bearing ketiminate ligands did, except OiPrAlMe 2 (2 fold lower catalytic activity). In addition, Al complexes with steric hindrance or electron-withdrawing groups in the ligands revealed the greater catalytic activity, and the chelating effect reduced the reactivity of ring-opening polymerization. [ABSTRACT FROM AUTHOR]

• Comparison study of CL polymerization by six-membered ring Al complexes. • Al complexes bearing aminophenolate ligands revealed the greatest catalytic activity. A series of 6-membered ring aluminum (Al) complexes bearing Schiff base, benzotriazole phenolate, aminophenolate, carboxamide phenolate, and carboxylate phenolate were synthesized, and their applications in ε-caprolactone (CL) polymerizations were studied. The decreasing catalytic rates for CL polymerization were ranked as follows: Al complexes bearing aminophenolate > benzotriazole phenolate > carboxylate phenolate > Schiff base > carboxamide phenolate. The Al complex bearing aminophenolate (LBu-prop) revealed an appreciably higher (10–100 fold) polymerization rate and a shorter induction period than the other 6-membered ring Al complexes in the CL polymerization. Further investigation of the steric effect in the phenolate ring of aminophenolate ligands demonstrated that Al complexes with the tert -butyl groups on 2,4 positions of the phenolate ring had the highest catalytic activity, followed by that of the cumyl groups, and it was also discovered that the hydrogen substituents were responsible for the largest decrease in the catalytic activity of Al complexes. The bulky substituents on the amino group increased the catalytic activity of associated Al complexes as well as the aminophenolate ligands with the third chelating atoms on the amino group. However, the aminophenolate ligands with the fourth chelating atoms on the amino group slightly decreased the catalytic activity. [ABSTRACT FROM AUTHOR]

A series of titanium (Ti) complexes bearing ONO-tridentate Schiff bases were synthesized and their application to the ring-opening polymerization of L-lactide and ε-caprolactone was studied. Ti complexes bearing ONO-tridentate Schiff bases revealed a greater catalytic activity compared to other previously synthesized Ti complexes bearing multi-dentate phenolate ligands. We hypothesize that using ONO-tridentate Schiff bases as ligands reduces the occupied space and increases the monomer coordination around the Ti center, thereby increasing catalytic activity. The electronic effect of the phenolate group on the polymerization rate was also studied, showing that electron-donating substituents on the ligands could drastically increase polymerization activity. [ABSTRACT FROM AUTHOR]

A series of lithium complexes bearing NNO-tridentate Schiff base ligands were successfully synthesized, characterized by X-ray crystallography, and investigated as catalysts for the ring opening polymerization of l -lactide. The electronic effects and steric bulk of the ligands coordinated to Li atoms were determined to greatly influence its catalytic properties. Li complexes with electron-donating or bulky substituents of ligands both revealed higher catalytic activities than did the electron-withdrawing groups during polymerization. Among the Li complexes, [L Bu -Li] 2 with the two tert -butyl groups exhibited the highest catalytic activity and outstanding controllability. [ABSTRACT FROM AUTHOR]

[Display omitted] In this study, a series of mononuclear complexes and dinuclear aluminum complexes bridged by 1,3- and 1,4-substituted phenyl ligands were synthesized, and their activities for the ring-opening polymerization (ROP) of ε-caprolactone (CL) were investigated. All the dinuclear aluminum complexes exhibited higher catalytic activity than did the corresponding mononuclear Al complexes (2–6-fold for the k obs values), and most of the dinuclear Al complexes bearing 1,3-substituted phenyl ligands exhibited higher activity than did the corresponding dinuclear Al complexes bearing 1,4-substituted phenyl ligands (1.5–3-fold for the k obs values). The only exceptions were the Al complexes bearing benzothiazole ligands, for which the dinuclear Al complex with 1,4-bis(benzothiazol-2-yl)benzene exhibited higher catalytic activity than did the corresponding 1,3- bis(benzothiazol-2-yl)benzene complex. This higher activity of the dinuclear Al complexes was attributed to one of the Al atoms in the dinuclear Al system being regarded as an electron-withdrawing group. This group influenced the other Al atom through associated aromatic ligands to enhance the catalytic activity for the ROP of CL. [ABSTRACT FROM AUTHOR]

Background Strategies combining anti-vascular therapy and vascular imaging may facilitate the prediction of early response and outcome in cancer treatment. Objective The aim of this study was to investigate the relationship between the tumor-associated vasculature in melanoma and to develop an approach for melanoma treatment by utilizing the free form and micelle form of the photosensitizer (PS) chlorin e6 in photodynamic therapy (PDT). Methods Green fluorescence protein (GFP) expressing B16-F10 melanoma cells were implanted into the mouse ear dermis. Ce6 in free form or in micelle form was administered via the tail vein. An OV100 imaging system was used to record the red fluorescence of Ce6 to obtain real-time vascular images in the GFP tumor. Results Compared to free Ce6, Ce6 linked to the micelle-nanocarrier depicted a much clearer vascular image and had an effective vascular destruction by PDT. Micelle Ce6 was localized in lysosomes and in the endoplasmic reticulum of cultured endothelial cells, implying an active endocytosis of the nano-carrier. Conclusion Micelle Ce6 can serve as a bifunctional PS for vascular imaging and PDT, which facilitates its delivery in the tumor microenvironment. [ABSTRACT FROM AUTHOR]

A series of titanium (Ti) compounds bearing 2,6-bis(o -hydroxyalkyl)pyridine ligands were synthesized and investigated as catalysts for the ring-opening polymerization of ε-caprolactone (CL) and L -lactide (LA). The Ti complexes with electron-withdrawing groups in pyridine rings or steric bulky groups in hydroxymethyl groups reduced the catalytic activity in CL and LA polymerizations, and Me L Ph -TiOPr 2 exhibited the highest catalytic activity ([CL] = 0.5 M, [CL]:[Cat] = 100:8, 60 °C, 7.5 h, conversion = 93%; [LA] = 0.5 M, [LA]:[Cat] = 100:8, 60 °C, 3.5 h, conversion = 98%). The density functional theory calculation results revealed that CL interacted with the ligand through weak hydrogen bonds, and then approached the Ti center. After being attacked by isopropyl oxide, the carbonyl group of CL bonded to the Ti center. After the rearrangement and ring opening of CL ring, CL was converted to poly-ε-caprolactone. Image 1 • Ti compounds bearing 2,6-bis(o -hydroxyalkyl)pyridine ligands were synthesized. • LA and CL polymerizations were investigated. • Me L Ph -TiOPr 2 exhibited the highest catalytic activity. [ABSTRACT FROM AUTHOR]

A series of aluminum complexes bearing heterocyclic amine ligands were synthesized, and their application in ε -caprolactone (CL) and L -Lactide (LA) polymerization and copolymerization were studied. The CL polymerization results revealed that ligands containing the higher electronegativity atom increased the polymerization rate of CL polymerization. Among these Al complexes, NON-AlMe 3 bearing benzofurazan ligand was the best catalyst in CL polymerization ([ NON-AlMe 3 ] = 10 mM, conversion = 94% after 4 min at room temperature). In LA polymerization, the catalytic trend of Al complexes was random, and NCN-AlMe 3 bearing 1-benzylbenzimidazole ligand was the best catalyst ([ NCN-AlMe 3 ] = 10 mM, conversion = 90% after 45 min at 80 °C). The selectivity of the production of a PLA- gradual -PCL copolymer could be controlled by different Al complexes. Our study revealed that the four-coordinated trimethyl Al complexes bearing heterocyclic amine ligands were easily synthesized and constitute an ideal catalyst design in CL polymerization. Image 1 • NON-AlMe 3 was the best catalyst in CL polymerization. • NCN-AlMe 3 was the best catalyst in LA polymerization. • PLA- gradual -PCL copolymer could be controlled by different Al complexes. [ABSTRACT FROM AUTHOR]

• 5-membered ring Mg complexes had higher activity in lactide polymerization. • Mg complexes with thiophene groups revealed the highest catalytic activity. • BnOH approaches LA through the hydrogen bond with phenolate, and then initiates LA. A series of magnesium complexes bearing 2-(arylideneamino)phenolate (forming 5-membered ring Mg complexes) and 2-((arylimino)methyl)phenolate (forming 6-membered ring Mg complexes) ligands were synthesized, and their application in the ring-opening polymerization of L -lactide (LA) was investigated. The Mg complexes with 5-membered rings exhibit a higher polymerization rate and controllability for polylactide production than those with 6-membered rings do (one-fold to three-fold for LA polymerization). The density function theory calculation results revealed that benzyl alcohol approaches LA through the hydrogen bond with phenolate oxygen, and then initiates LA, with the proton transferring to phenolate oxygen to form the LA-OBn adduct. The LA-OBn adduct was activated using the proton present on phenolate oxygen to open the ring of the LA-OBn adduct. Moreover, the LA polymerization using L5ThioMg as a catalyst needs to overcome a 17.7 kcal/mol activation free energy that is lower than that of L6ThioMg (21.0 kcal/mol) [ABSTRACT FROM AUTHOR]

A series of pyridine and polypyridine-zinc complexes were synthesized, and their application in ε-caprolactone and l -lactide polymerization was studied. In ε-caprolactone polymerization, zinc complexes bearing 1,10-phenanthroline derivatives exhibited a higher polymerization rate than did diethyl zinc (2–10 times). In l -lactide polymerization, zinc complexes bearing 1,10-phenanthroline derivatives exhibited a considerably higher polymerization rate than did diethyl zinc (2–220 times). According to density functional theory results, the ortho -hydrogens of polypyridine ligand can co-activate the carbonyl group of monomers with zinc metal center to increase the catalytic activity of zinc catalysts. Image 1 • The polypyridne-zinc complexes were synthesized. • 1,10-Phenanthroline derivatives enhanced the catalytic activity of Zn complexes. • Hydrogens of polypyridine co-activate the carbonyl group of monomers. [ABSTRACT FROM AUTHOR]

The ring-opening polymerizations of ε-caprolactone (CL) using 5- and 6-membered ring Zn complexes bearing Schiff base as catalysts were comparatively studied. The 5-membered ring Zn complexes exhibited a considerably higher polymerization rate than the 6-membered ring Zn complexes (2–12 fold for CL polymerization) did. X-ray data revealed that 5-membered ring L 5-Ph 2 Zn creates larger empty space around the Zn center than 6-membered ring L 6-Bn 2 Zn. This allows higher interaction between the initiator and Zn complex and easy CL coordination. Image 1 • The 5-membered ring Zn complexes exhibited a considerably higher polymerization rate. • X5-membered ring L5-Ph 2 Zn creates larger empty space around the Zn center than 6-membered ring L6-Bn 2 Zn [ABSTRACT FROM AUTHOR]

Main-group metal-based catalysts have attracted considerable attentions due to their complementary reactivities to transition metals. In searching for the catalytic application of heavy divalent Group 14 derivatives, we came to discover that the benzannulated N -heterocyclic plumbylene (1) could serve as an effective catalyst for ring-opening polymerization of l -lactide (L- LA) at room temperature. In the presence of benzyl alcohol (BnOH), 97% conversion of L- LA was accomplished in 10 min under a catalyst loading of merely 0.3 mol% ([LA]:[1]:[BnOH] = 400:1.2:1.2, [1] = 1.2 mM). Compared to the polymeric plumbylene ([Pb(μ -O i Pr) 2 ∞), the excellent catalytic activity of 1 at ambient temperature may be ascribed to the steric and electronic stabilizations of the Pb2+ center by the organic backbone. Thus, thermal activation is no longer required to expose the Lewis acidic metal center for polymerization. Image 1 • N -Heterocyclic plumbylene is an efficient catalyst in ring-opening polymerization of l -lactide. • 97% conversion of L- LA was accomplished in 10 min under a catalyst loading of merely 0.3 mol%. • N -Heterocyclic plumbylene reveals outstanding controllability in l -lactide polymerization. [ABSTRACT FROM AUTHOR]