Design and synthesis of copper() malonates with N,N′-containing linkers

Knowledge-based approach to the design of coordination polymers with a given architecture in general requires knowledge of regularities between the local coordination of metal atoms (or polynuclear metal-containing units), coordination modes of all ligands in a complex, and the entire framework topology. The effect of the local coordination on the dimensionality and topology of the underlying nets was demonstrated on the example of 4,4′-bipyridine (bipy), 1,2-bis(4-pyridyl)ethylene (bpe) and 1,2-bis(4-pyridyl)ethane (bpa) containing copper( ii ) malonates. The most abundant networks were evaluated for these compounds and compared with those for previously analyzed and synthesized zinc( ii )-containing analogs. Eight novel complexes, namely [Cu(bpe)(mal)]·2CH 3 CN, [Cu 4 (bipy) 4 (Me 2 mal) 4 (H 2 O) 5 ]·3H 2 O, [Cu(bpe)(HMe 2 mal) 2 ]·H 2 O, [Cu(bpe)(Me 2 mal)]·H 2 O, [Cu 4 (bpe) 3 (Et 2 mal) 4 ]·5H 2 O, [Cu 4 (bpa) 3 (Et 2 mal) 4 ]·5.5H 2 O, [Cu(bpe)(Amal)]·0.25H 2 O, and [Cu(bpa)(Amal)]·0.25H 2 O (H 2 mal = malonic acid, H 2 Me 2 mal = dimethylmalonic acid, H 2 Et 2 mal = diethylmalonic acid, H 2 Amal = allylmalonic acid), were synthesized and characterized. Four of them realized the square lattice topology ( sql ) of their underlying nets, which is highly abundant for copper( ii ) malonates with N,N′-containing linkers but rarely occurs in similar complexes based on other transition metals. The UV-sensitivity of the bpe-containing complexes as well as of the previously reported complex [Cu 4 (bpe) 3 (mal) 4 ]·6H 2 O was studied; and [Cu 4 (bpe) 3 (mal) 4 ]·6H 2 O was found to undergo a single-crystal-to-single-crystal photoinitiated [2 + 2] cycloaddition reaction to [Cu 4 (bpe)(tpcb)(mal) 4 ]·6H 2 O (tpcb = rctt -1,2,3,4-tetrakis(pyridin-4-yl)cyclobutane). The dc-magnetic measurements of the complexes [Cu(bpe)(Me 2 mal)]·H 2 O, [Cu(bpe)(Amal)]·0.25H 2 O and [Cu(bpa)(Amal)]·0.25H 2 O indicated the presence of very weak antiferromagnetic intermolecular interactions. Using EPR spectroscopy, it was shown that the distortion of the polyhedron of the copper( ii ) atom corresponded to a change in the anisotropy of the g -tensor. Effect of the metal coordination on the periodicity and topology of coordination polymers is discussed on the example of copper( ii ) malonates with N,N′-containing linkers as compared with zinc( ii ) analogs.