SPONTANEOUS FORMATION OF A 1D-COORDINATION POLYMER WITH HELIX STRUCTURE STARTING FROM (S)-PYROGLUTAMIC ACID AND COPPER(II) ACETATE

Reaction of a methanolic copper(II) acetate solution and (S)-methoxyca rbonyl pyrrolidine (6) (HL3) in the presence of triethylamine leads to a mixture of two charges of crystals that are easy to distinguish vis ually. According to X-ray crystal structure analyses the products are the pseudo dimeric molecular complex [CuL2(3)].[CuL2(4)] (12) and the helical 1D-coordination polymer ([CuL2(3)].1/2Et2O)infinity (3). Prere quisite for the formation of the centrosymmetric complex 12 is the par tial inversion of [(S),(S)-CuL2(3)] (10) (HL3 = 6) to [(R),(R)-CuL2(4) ] (11) (HL4 = 7), induced by triethylamine. Complex 12 is formed via l inking of monomers 10 and 11 across two of the four available MeO oxyg ens. The unit cell of the 1D-coordination polymer 3 is composed of two almost identical helix strands (LAMBDA)-Cu(1)-3 and (DELTA)-Cu(2)-3. Each strand is generated by a set of very similar monomeric building b locks Cu(1)-10 and Cu(2)-10. The structure data of (LAMBDA)-Cu(1)-3 an d (DELTA)-Cu(2)-3, reveal that each of the Cu(1) and Cu(2) atoms is li nked across the N(28) atoms of only one neighbouring cyano group of th e monomers 10. The 1D-coordination polymer (LAMBDA)-Cu(1)/(DELTA)-Cu(2 )-3 cocrystallises with diethyl ether to form a clathrate.