A New Family of Renewable Thermosets: Kraft Lignin Poly-adipates.

Thermosetting polymeric materials have advantageous properties and are therefore used in numerous applications. In this study, it was hypothesized and ultimately shown that thermosets could be derived from comparably sustainable sub-components. A two-step procedure to produce a thermoset comprising of Kraft lignin (KL) and the cross-linker adipic acid (AdA) was developed. The cross-linking was activated by means of an acetylating agent comprising isopropenyl acetate (IPA) to form a cross-linking mixture (CLM). The cross-linking was confirmed by FTIR and solid-state NMR spectroscopy, and the esterification reactions were further studied using model compounds. When the KL lignin was mixed with the CLM, partial esterification occurred to yield a homogeneous viscous liquid that could easily be poured into a mold, as the first step in the procedure. Without any additions, the mold was heated and the material transformed into a thermoset by reaction of the two carboxylic acid-derivatives of AdA and KL in the second step.

A naphthalene-fused dimer of an anti-aromatic expanded isophlorin.

We report the first synthesis of a covalent expanded isophlorin dimer from two 24-π doubly S-confused sapphyrin-like pentathiaisophlorins. It exhibits marginal peripheral aromaticity rather than strong global diatropicity or paratropicity and weak intermacrocycle electronic communication. Quantum chemical methods discern that cross-conjugation is responsible for these unusual electronic features.

The synthesis and characterization of the meso-meso linked antiaromatic tetraoxa isophlorin dimer.

The first synthesis of meso-meso linked antiaromatic isophlorin has been described. The synthetic pathway is different from the routinely employed oxidative coupling of meso free porphyrin into its dimer and oligomers. Spectroscopic and structural analyses revealed paratropic ring current effects and each unit was found to be orthogonal to each other.

Non-covalent composites of antiaromatic isophlorin-fullerene.

Cocrystallates of fullerene C60 and antiaromatic planar tetraoxaisophlorins have been characterized by single crystal X-ray diffraction analysis. The ring-juncture bonds of C60 are found to be at a very close distance to the plane of the antiaromatic isophlorins. NMR measurements and MALDI-TOF mass spectrometry show that this interaction can persist in both solution and gaseous states, which can be attributed to van der Waals dispersion forces.

Metal assisted cyclodimerization of doubly N-confused dipyrrins into planar aza-heptalenes.

Metal salts cyclodimerize doubly N-confused dipyrrin into a nornorrole type macrocycle, with a bipyrrolic unit at its center. It also represents an unusual aza-heptalene structure with fused bicyclic seven membered rings. The fused rings can have one or two C-N bonds between the dipyrrin units in the cyclodimer. The (1)H NMR spectrum of these molecules displays aromatic character, rather than antiaromatic behaviour expected of nornorrole, and planar conformation in the solid state.