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

CrystEngComm. 2023. Vol. 25. No. 19. P. 2859–2870.

Ekaterina N. Zorina-Tikhonova, Chistyakov A., Novikova V., Knyazev D., Gogoleva N., Blinou D., Efimov N., Dorovatovskii P., Kiskin M., Eremenko I., Vologzhanina A.

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 metalcontaining
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)]·2CH3CN, [Cu4(bipy)4(Me2mal)4(H2O)5]·3H2O,
[Cu(bpe)(HMe2mal)2]·H2O, [Cu(bpe)(Me2mal)]·H2O, [Cu4(bpe)3(Et2mal)4]·5H2O, [Cu4(bpa)3(Et2mal)4]·5.5H2O,
[Cu(bpe)(Amal)]·0.25H2O, and [Cu(bpa)(Amal)]·0.25H2O (H2
mal = malonic acid, H2Me2mal =
dimethylmalonic acid, H2Et2mal = diethylmalonic acid, H2Amal = 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 [Cu4(bpe)3(mal)4]·6H2O was studied; and [Cu4(bpe)3(mal)4]·6H2O
was found to undergo a single-crystal-to-single-crystal photoinitiated [2 + 2] cycloaddition reaction to
[Cu4(bpe)(tpcb)(mal)4]·6H2O (tpcb = rctt-1,2,3,4-tetrakis(pyridin-4-yl)cyclobutane). The dc-magnetic
measurements of the complexes [Cu(bpe)(Me2mal)]·H2O, [Cu(bpe)(Amal)]·0.25H2O and [Cu(bpa)(Amal)]·0.25H2O
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

Keywords: Carboxylates, карбоксилаты, malonates, copper complexes, малонаты, комплексы меди