Novel Dinuclear Redox‐isomeric Complexes with a Tetrapodal Pyridine‐based Ligand

Tris‐o‐semiquinonato cobalt complexes react with a tetrapodal pyridine‐derived ligand to form dinuclear cobalt compounds of general formula (OMP)[CoQ₂]₂, where OMP = 2,2′‐(pyridine‐2,6‐diyl)bis(N¹,N¹,N³,N³‐tetramethylpropane‐1,3‐diamine), Q = mono‐ or dianion of 3,6‐di‐tert‐butyl‐o‐benzoquinone (complex 1 ) and it derivatives: 3,6‐di‐tert‐butyl‐4,5‐N,N′‐piperazino‐o‐benzoquinone (complex 2 ), and 3,6‐di‐tert‐butyl‐4‐Cl‐o‐benzoquinone (complex 3 ). Single crystal X‐ray crystallography of 1 and 3 indicates two bis‐quinonato cobalt units bound by an OMP ligand, which acts as a bridge. Each central cobalt atom is chelated by one N¹,N¹,N³,N³‐tetramethylpropane‐1,3‐diamine and two o‐quinonato fragments. The nitrogen atom of the pyridine ring is uncoordinated. All complexes were characterized by NIR‐IR and EPR spectroscopy, precise adiabatic vacuum calorimetry, and by variable‐temperature magnetic susceptibility measurements. All data indicate a reversible thermally driven redox‐isomeric (valence tautomeric) transformation in the solid state for all complexes.     

Optimal descriptors as a tool to predict the thermal decomposition of polymers

Quantitative structure-property relationship for the thermal decomposition of polymers is suggested. The data on architecture of monomers is used to represent polymers. The structures of monomers are represented by simplified molecular input-line entry system. The average statistical quality of the suggested quantitative structure-property relationships for prediction of molar thermal decomposition function $\hbox {Y}_{\mathrm{d},1/2}$ is the following: $\hbox {r}^{2}=0.970 \pm 0.01$ and $\hbox {RMSE}=4.71\pm 1.01\,(\hbox {K}\times \hbox {kg}\times \hbox {mol}^{-1})$ .     

Linear polyamides from L‐malic acid and alkanediamines

A series of linear polyamides (PnMLM) derived from O‐methyl‐protected L ‐malic acid and 1,n‐alkanediamines with even n values ranging from 4 to 12 were prepared and fully characterized. L ‐Malic acid entered in the chain with a random orientation rendering essentially aregic polymers. PnMLM displayed optical rotation consistent with the content of the polymer in malic units, and they all were crystalline with melting points ranging from 158 to 188 °C and glass‐transition temperatures varying from 37 to 70 °C. PnMLM appeared to be fairly stable to heat with thermal decomposition starting close to 300 °C. Hydrolytic degradation of PnMLM at 37 °C was slow, but the process was significantly faster at 70 °C. Thermal degradation took place with the formation of cyclic malimides in the residual polymer and released the 1,n‐alkanediamine. However, hydrolytic degradation took place in a first stage with the formation of open chains of carboxylic‐ and amine‐ended oligomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1566–1575, 2004     

Carbohydrate‐based copolyesters made from bicyclic acetalized galactaric acid

Mixtures of the dimethyl esters of adipic acid and 2,3:4,5‐di‐O‐methylene‐galactaric acid (Galx) were made to react in the melt with either 1,6‐hexanediol or 1,12‐dodecanediol to produce linear polycyclic copolyesters with aldarate unit contents varying from 10 up to 90 mole %. The copolyesters had weight–average molecular weights in the ～35,000–45,000 g mol^?1 range and a random microstructure, and were thermally stable up to nearly 300 °C. They displayed T_g in the ‐50 to ‐7 °C range with values largely increasing with the content in galactarate units. All the copolyesters were semicrystalline with T_m between 20 and 90 °C but only those made from 1,12‐dodecanediol were able to crystallize from the melt at a crystallization rate that decreased as the contents in the two comonomers approached each other. Copolyesters containing minor amounts of galactarate units adopted the crystal structure characteristic of aliphatic polyesters but a new crystal polymorph was formed when the cyclic sugar units became the majority. Stress–strain parameters were sensitively affected by composition of the copolyesters with the mechanical behavior changing from flexible/ductile to stiff/brittle with the replacement of adipate units by the galactarate units. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Influence of core configuration and arm structure on solution properties of new thermosensitive star-shaped poly(2-alkyl-2-oxazolines)

New thermoresponsive star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx) and poly(2-ethyl-2-oxazoline) (PEtOx) with arm grafting to upper rim of calix[8]arene core were synthesized and studied in aqueous solutions by light scattering and turbidimetry methods. The solution behavior was compared with that for polyoxazoline stars with varying positions of arm grafting, i.e., to lower rim of calix[8]arene. The observed growth of the phase separation temperature for PiPrOx as compared to PEtOx is explained by different dehydration temperatures of ethyl- and isopropyloxazoline units. The phase separation temperatures decrease after the changeover from lower rim grafting to upper rim one due to varying configurations of calix[8]arene.     

Use of quasi-SMILES to model biological activity of “micelle–polymer” samples

The basic task of the drug discovery is the establishing of molecular structure of new pharmaceutical agents. To define the molecular structure is only half of the way to new drug. The transport of active molecules to appropriate targets in an organism should be elucidated in details. The selection of polymeric structures playing the role of basis for transport of therapeutic agents into the body is one of the ways to solve the task. Drug loading capacity (DLC) and critical micelle concentration (CMC) are measures of ability of “polymer–micelle” systems to be suitable for the process of the transport of therapeutic agents into an organism. Polymeric micelles are a type of complex multi-phase and multicomponent chemical process and can be used to transport drug into an organism. Prediction of ability of “micelle–polymer” systems to be a tool for transport of therapeutic agents to targets in organism is an important task. Models, which are a mathematical function of available eclectic information about architecture of micelles and polymers, are suggested. The eclectic data are represented via the so-called quasi-simplified molecular input-line entry system (SMILES), which are analogy of traditional SMILES. The quasi-SMILES contain some additional information besides the molecular architecture (physicochemical and biochemical conditions). Predictive potential of these models is good.