Poly(lactic acid) (PLA) is a promising biodegradable polymer based on renewable resources. This paper describes scale-up studies to synthesize high molecular weight PLA (>100'000 g/mol) in five steps from commercial lactic acid. The first four steps of this process consist of synthesizing
a highly pure precursor, lactide, which can be converted into a high molecular PLA by ring opening polymerization (ROP). We produced PLA with a molecular weight of 109'000 g/mol using this strategy.
Dithienylethene-phenanthroline ligands as new photochromic systems are described. The photochemical and photophysical properties are strongly influenced by the substituents on the thiophene moiety. The photochromic properties are lost, if one or two methyl groups in position 2 and/or
2' of the target molecules (2o, 3o, 4o) are replaced by isopropyl groups. Replacement of a methyl group by a phenyl group in position 5 and/or 5' shifts the absorption maxima from 514 nm to 575 nm for the free ligand (1c, 2c) and from 530 nm to 613 nm for
the corresponding ruthenium complex (Ru(1c), Ru(2c)) in its closed form. Unfortunately, the photochromic unit in its closed form can be reopened by a back reaction in the dark at room temperature. Complex Ru(2o) shows an emission with a maximum at
608 nm. The emission is quenched if the metal complex is in its closed form (Ru(2c)). Fatigue resistance is better for complex Ru(2o) than for the free ligand (2o).
Abstract:The synthesis of an unsymmetrically substituted 1,10-phenanthroline ligand and its corresponding ruthenium(II) complex is reported. Suzuki coupling has been employed under different conditions to get the target ligand.
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