The binuclear complex NiII2L(H2O)2(ClO4)2
(1) and the neutral tetranuclear bimetallic compounds [{MIII(phen)(CN)4}2{NiII2L(H2O)2}]·2CH3CN with M = Fe (2) and Cr (3)
[H2L = 11,23-dimethyl-3,7,15,19-tetraazatricyclo[19.3.1.19,13]hexacosa-2,7,9,11,13(26),14,19,21(25),22,24-decaene-25,26-diol] have been synthesized and the structures of 2 and 3 determined by single crystal X-ray diffraction. 2 and 3 are isostructural compounds whose structure is made up of centrosymmetric binuclear cations [Ni2(L)(H2O)2]2+ and two peripheral [M(phen)(CN)4]− anions [M = Fe (2) and Cr (3)] acting as monodentate ligands towards the nickel atoms through one of their four cyanide nitrogen atoms. The environment of the metal atoms in 2 and 3 is six-coordinated: two phen-nitrogen and four cyanide-carbon atoms at the iron and chromium atoms and a water molecule, one cyanide-nitrogen and two phenolate-oxygens and two imine-nitrogens from the binucleating ligand L2− at the nickel atom build distorted octahedral surroundings. The values of the Fe⋯Ni and Cr⋯Ni separations through the single cyanide bridge are 5.058(1) and 5.174(2)
Å respectively, whereas the Ni–Ni distances across the double phenolate bridge are 3.098(2)
(2) and 3.101(1)
Å
(3). The magnetic properties of 1–3 have been investigated in the temperature range 1.9–290 K. The magnetic behaviour of 1 corresponds to that of an antiferromagnetically coupled nickel(II) dimer with J
=
−61.0(1) cm−1, the Hamiltonian being defined as Ĥ
=
−J ŜA·ŜB. An overall antiferromagnetic behaviour is observed for 2 and 3 with a low-lying singlet spin state. The values of the intramolecular magnetic couplings are JFe–Ni
=
+17.4(1) cm−1 and JNi–Ni(a)
=
−44.4(1) cm−1 for 2 and JCr–Ni
=
+11.8(1) cm−1 and JNi–Ni(a)
=
−44.6(1) cm−1 for 3
[Ĥ
=
−JM–Ni
(ŜM·ŜNi
+
ŜMa·ŜNia)
−JNi–NiaSNiSNia]. Theoretical calculations using methods based on density functional theory (DFT) have been employed on 2 in order to analyze the efficiency of the exchange pathways involved and also to substantiate the exchange coupling parameters.