Three new trinuclear heterometallic nickel(II)-manganese(II) complexes, [(NiL) 2 Mn(NCS) 2 ] (1), [(NiL) 2 Mn(NCO) 2 ] (2), and [{NiL(EtOH)} 2 Mn(NO 2 ) 2 ]·2EtOH (3), have been synthesized by using [NiL] as the so-called "ligand complex" [where H 2 L = N,NЈ-bis(salicylidene)-1,3-propanediamine] and have been structurally characterized. Crystal structure analyses revealed that complexes 1 and 2 are angular trinuclear species, in which two terminal four-coordinate square planar [NiL] moieties are coordinated to a central Mn II through double phenoxido bridges. The Mn II is in a six-coordinate distorted octahedral environment that is bonded additionally to two mutually cis nitrogen atoms of terminal thiocyanate (in 1) and cyanate (in 2). In complex 3, in addition to the double phenoxo bridge, the two terminal Ni II ions are linked to the central [a]

Two heterometallic coordination polymers (CPs) have been prepared using [Ni(II)L]2Co(II) (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine) as nodes and dicyanamido spacers by varying the solvent for synthesis. Structural characterizations revealed that methanol assisted the formation of a two-dimensional (4,4) connected rhombic grid network of [(NiL)2Co(NCNCN)2]∞ (1a) whereas relatively less polar acetonitrile afforded a different superstructure {[(NiL)2Co(NCNCN)2]·CH3CN}∞ (1b) with a two-dimensional (4,4) connected square grid network. The presence of acetonitrile molecules in the structure of 1b seems to change the spatial orientation of the terminal metalloligands [NiL] from pseudo-eclipsed in 1a to staggered-like in 1b around the central Co(II). These structural changes in the nodes together with the conformationally flexible dicyanamido spacers, which are cis coordinated to the Co(II) in both trinuclear units, led to the differences in the final 2D network. Variable-temperature magnetic susceptibility measurements revealed that this supramolecular isomerism led to a drastic transition from spin-frustrated antiferromagnetism for 1a to a dominant ferromagnetic behaviour for 1b. The geometrical differences in Ni2Co coordination clusters (CCs) which are scalene triangular in 1a but nearly linear in 1b, are held responsible for the changes of the magnetic properties. The DFT calculations of exchange interactions between metal centres provide a clear evidence of the role played by the fundamental geometrical factors on the nature and magnitude of the magnetic coupling in these pseudo-polymorphic CPs.

Five new trinuclear heterometallic Cu(II)-Mn(II) complexes [(CuL)2Mn(O2CPh)2] (1), [(CuL)2Mn(N3)2] (2), [(CuL)2Mn(NCO)2] (3), [(CuL)2Mn(NO3)2] (4) and [(CuL)2Mn(Sal)2]·CH2Cl2 (5) have been synthesized with the di-Schiff base ligand H2L (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine and Sal = salicylate). These complexes with different anionic co-ligands have been synthesized to attain a large variation in phenoxido bridging angles and to investigate its consequence on magnetic properties. Single crystal X-ray diffraction analyses reveal that complexes 1, 2, 4 and 5 are linear, whereas 3 has an angular geometry. Variable temperature magnetic susceptibility measurements suggest that all five complexes possess an overall antiferromagnetic interaction between Cu(II) and Mn(II) ions, which results in a final ferrimagnetic ground state with spin 3/2 in the Cu(II)-Mn(II)-Cu(II) trinuclear structure. The weakest antiferromagnetic interaction (J(Cu-Mn) = -7.0 cm(-1)) is observed for 2 having the lowest value of the Cu-O-Mn angle (92.0°), while the strongest antiferromagnetic interaction (J(Cu-Mn) = -26.5 cm(-1)) is observed for 3 having the largest Cu-O-Mn angle (101.4°). Complexes 1, 4 and 5 show average Cu-O-Mn angles of 98.2°, 97.6° and 97.7°, respectively, that lead to intermediate antiferromagnetic interactions (J(Cu-Mn) = -9.6, -9.7, -9.3 cm(-1) respectively).

Three new trinuclear heterometallic Ni(II)-Mn(II) complexes have been synthesized using a [NiL] metalloligand, where H2L = N,N'-bis(salicylidene)-1,3-propanediamine. The complexes [(NiL)2Mn(OCnn)2(CH3OH)2]·CH3OH (1), [(NiL)2Mn(OPh)2(CH3OH)2][(NiL)2Mn(OPh)2]·H2O (2), and [(NiL)2Mn(OSal)2(CH3OH)2]·2[NiL] (3) (where OCnn = cinnamate, OPh = phenylacetate, OSal = salicylate) have been structurally characterized. In all three complexes, in addition to the double phenoxido bridge, the two terminal Ni(II) atoms are linked to the central Mn(II) by means of a syn-syn bridging carboxylate, giving rise to a linear structure. Complexes 1 and 2 with Ni-O-Mn angles of 97.24 and 96.43°, respectively, exhibit ferromagnetic interactions (J(Ni-Mn) = +1.38 and +0.50 cm(-1), respectively), whereas 3 is antiferromagnetic (J(Ni-Mn) = -0.24 cm(-1)), having an Ni-O-Mn angle of 98.51°. DFT calculations indicate that there is a clear magneto-structural correlation between the Ni-O-Mn angle and J(Ni-Mn) values, which is in agreement with the experimental results.

Reaction of manganese(II) with the electron-deficient ligand 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine (pbptz) leads to distinct coordination networks whose topologies are influenced by the nature of the anions used.As anticipated, the linear ditopic ligand pbptz is involved in various types of supramolecular p interactions, i.e. p … p, lone pair … p and C-H … p interactions, which clearly play a role in the formation of the different solid-state architectures obtained, as shown by DFT calculations.