It is a challenge to synthesize materials that possess the properties of biological muscles-strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as -20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl-iron one, and two weaker carboxamido-iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron-ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material.
Reactions of [Fe(TPFPP)] (TPFPP = meso-tetrakis(pentafluorophenyl)porphyrinato dianion) with diazo compounds N(2)C(Ph)R (R = Ph, CO(2)Et, CO(2)CH(2)CH=CH(2)) afforded [Fe(TPFPP)(C(Ph)R)] (R = Ph (1), CO(2)Et (2), CO(2)CH(2)CH=CH(2) (3)) in 65-70% yields. Treatment of 1 with N-methylimidazole (MeIm) gave the adduct [Fe(TPFPP)(CPh(2))(MeIm)] (4) in 65% yield. These new iron porphyrin carbene complexes were characterized by NMR and UV-vis spectroscopy, mass spectrometry, and elemental analyses. X-ray crystal structure determinations of 1.0.5C(6)H(6).0.5CH(2)Cl(2) and 4 reveal Fe=CPh(2) bond lengths of 1.767(3) (1) and 1.827(5) A (4), together with large ruffling distortions of the TPFPP macrocycle. Complexes 2 and 4 are reactive toward styrene, affording the corresponding cyclopropanes in 82 and 53% yields, respectively. Complex 1 is an active catalyst for both intermolecular cyclopropanation of styrenes with ethyl diazoacetate and intramolecular cyclopropanation of allylic diazoacetates. Reactions of 2 and 4 with cyclohexene or cumene produced allylic or benzylic C-H insertion products in up to 83% yield.
A stiff and healable polymer is obtained by using the dynamic-covalent boroxine bond to crosslink PDMS chain into 3D networks. The as-prepared polymer is very strong and stiff, and can bear a load of more than 450 times its weight. When damaged, it can be completely healed upon heating after wetting.
The pyridyltetrazolate ligand formed in situ from NaN3 and 3‐cyanopyridine in the presence of ZnCl2 or CdCl2 in water affords acentric (1) or chiral (2) coordination polymers, respectively. The corresponding reaction of ZnCl2 with 4‐cyanopyridine gives acentric 3 (not shown). Compounds 1–3 are second harmonic generation active.
Hydrolysis of cisplatin, the most widely used anticancer drug in the world, is believed to be the key activation step before the drug reaching its intracellular target DNA. To obtain an accurate hydrolysis theory for this important class of square-planar Pt(II) complexes, three typical reactions, i.e., the first and second hydrolyses of cisplatin and the hydrolysis of [Pt(dien)Cl](+) (dien = diethylenetriamine), were studied at the experimental temperature with the solvent effect using mPW1PW91/SDD from a comprehensive methodological study on the Hartree-Fock (HF) ab initio method, electron correlation methods, pure density functional theory (DFT) methods, and hybrid HF-DFT methods with several basis sets. The true five stationary states in the second-order nucleophilic substitution (S(N)2) pathway for the hydrolysis process, namely, reactant (R) --> intermediate 1 (I1) --> TS --> intermediate 2 (I2) --> product (P) were obtained and characterized theoretically for the first time. The most remarkable structural variations and the associated atomic charge variations in the hydrolysis process were found to occur in the equatorial plane of the five-coordinate trigonal-bipyramidal (TBP)-like structures of I1, TS, and I2. The reaction with the TS structure of smaller L-M-E angle and more lengthened M-L and M-E bonds was found to have a smaller Gibbs free energy change and accordingly the better hydrolysis yield. It is found that the sum of the three concentric angles in the TBP's equator is near 360 degrees in I1 and I2 and is almost 360 degrees in TS in each reaction. The associated energy profiles again demonstrated a typical S(N)2 reaction curve. The computed forward and backward reaction enthalpy (Delta H(++)) and reaction entropy (Delta S(++)) in the rate-determining step I1 --> TS --> I2 are in good agreement with the experiments. Natural bonding orbital population analysis shows that the charge-separating extent follows the same order of Delta G in studied reactions. Comparing with the computational results of gas-phase reactions, it can be concluded that the solvent effect should be considered to obtain an accurate hydrolysis picture. The most affected structural parameters after solvation are related to the equatorial plane of the TBP-like geometry. The results provide theoretical guidance on detailed understanding on the mechanism of the hydrolysis of cisplatin, which could be useful in the design of novel Pt-based anticancer agents.
Based upon the (3,6)-connected metal-organic framework {Cu(L1)·2H(2)O·1.5DMF}(∞) (L1 = 5-(pyridin-4-yl)isophthalic acid) (SYSU, for Sun Yat-Sen University), iso-reticular {Cu(L2)·DMF}(∞) (L2 = 5-(pyridin-3-yl)isophthalic acid) (NJU-Bai7; NJU-Bai for Nanjing University Bai group) and {Cu(L3)·DMF·H(2)O}(∞) (L3 = 5-(pyrimidin-5-yl)isophthalic acid) (NJU-Bai8) were designed by shifting the coordination sites of ligands to fine-tune pore size and polarizing the inner surface with uncoordinated nitrogen atoms, respectively, with almost no changes in surface area or porosity. Compared with those of the prototype SYSU, both the adsorption enthalpy and selectivity of CO(2) for NJU-Bai7 and NJU-Bai8 have been greatly enhanced, which makes NJU-Bai7 and NJU-Bai8 good candidates for postcombustion CO(2) capture. Notably, the CO(2) adsorption enthalpy of NJU-Bai7 is the highest reported so far among the MOFs without any polarizing functional groups or open metal sites. Meanwhile, NJU-Bai8 exhibits high uptake of CO(2) and good CO(2)/CH(4) selectivity at high pressure, which are quite valuable characteristics in the purification of natural gases.
Two octacyanometallate-based clusters, {CoII9[WV(CN)8]6.(CH3OH)24}.19H2O (1) and {CoII9[MoV(CN)8]6.(CH3OH)24}.4CH3OH.16H2O (2), have been synthesized. Both complexes show the single-molecule magnet behavior.
The synthesis and spectroscopic properties of a series of boron-free meso-aryl-substituted [14]triphyrin(2.1.1) compounds containing either peripheral bicyclo[2.2.2]octadiene (BCOD) (2a−c) or benzene rings (3a−c) (aryl = phenyl a, 4-fluorophenyl b, and 4-methylbenzoatephenyl c) are reported. These compounds represent the first examples of free-base contracted porphyrinoids with 14 π-electron aromatic systems containing only the standard pyrrole and isoindoline moieties of the porphyrins and tetrabenzoporphyrins.
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