[M II (H 2 dapsc)]-[Cr(CN) 6 ] (M = Mn, Co) Chain and Trimer Complexes: Synthesis, Crystal Structure, Non-Covalent Interactions and Magnetic Properties.

Four new heterometallic complexes combining [M II (H 2 dapsc)] 2+ cations with the chelating H 2 dapsc {2,6-diacetylpyridine-bis(semicarbazone)} Schiff base ligand and [Cr(CN) 6 ] 3- anion were synthesized: {[M II (H 2 dapsc)]Cr III (CN) 6 K(H 2 O) 2.5 (EtOH) 0.5 } n ·1.2 n (H 2 O), M = Mn ( 1 ) and Co ( 2 ), {[Mn(H 2 dapsc)] 2 Cr(CN) 6 (H 2 O) 2 }Cl·H 2 O ( 3 ) and {[Co(H 2 dapsc)] 2 Cr(CN) 6 (H 2 O) 2 }Cl·2EtOH·3H 2 O ( 4 ). In all the compounds, M(II) centers are seven-coordinated by N 3 O 2 atoms of H 2 dapsc in the equatorial plane and N or O atoms of two apical -CN/water ligands. Crystals 1 and 2 are isostructural and contain infinite negatively charged chains of alternating [M II (H 2 dapsc)] 2+ and [Cr III (CN) 6 ] 3- units linked by CN-bridges. Compounds 3 and 4 consist of centrosymmetric positively charged trimers in which two [M II (H 2 dapsc)] 2+ cations are bound through one [Cr III (CN) 6 ] 3- anion. All structures are regulated by π-stacking of coplanar H 2 dapsc moieties as well as by an extensive net of hydrogen bonding. Adjacent chains in 1 and 2 interact also by coordination bonds via a pair of K + ions. The compounds containing Mn II ( 1 , 3 ) and Co II ( 2 , 4 ) show a significant difference in magnetic properties. The ac magnetic measurements revealed that complexes 1 and 3 behave as a spin glass and a field-induced single-molecule magnet, respectively, while 2 and 4 do not exhibit slow magnetic relaxation in zero and non-zero dc fields. The relationship between magnetic properties and non-covalent interactions in the structures 1 - 4 was traced.