Single-ion magnet behaviour in mononuclear and two-dimensional dicyanamide-containing cobalt(II) complexes

摘要: Three cobalt(II) complexes of formulae [Co(dca)2(bim)4] (1), [Co(dca)2(bim)2]n (2) and [Co(dca)2(bmim)2]n (3) [dca = dicyanamide, bim 1-benzylimidazole bmim 1-benzyl-2-methylimidazole] were prepared structurally analyzed by single-crystal X-ray crystallography. Compound 1 is a mononuclear species where the ion six-coordinate with four molecules in equatorial positions [Co–Nbim 2.1546(15) 2.1489(15) A] two trans-positioned dca ligands [Co–Ndca 2.1575(18) axial sites somewhat distorted octahedral surrounding. The structures 2 3 consist two-dimensional grids ions each metal atom linked to other centres single bridges exhibiting μ1,5-dca coordination mode 2.190(3)–2.220(3) 2.127(3)–2.153(3) A (3)]. Two trans-coordinated (2)/bmim achieve six-coordination around 2.128(3)–2.134(4) Co–Nbmim 2.156(3)–2.163(39) values cobalt–cobalt separation through are 8.927(2) 8.968(2) 8.7110(5) 8.7158(5) 3. Magnetic susceptibility measurements for 1–3 temperature range 2.0–300 K reveal that these compounds behave as magnetically isolated high-spin significant orbital contribution magnetic moment. Alternating current (ac) show frequency dependence out-of-phase under static applied fields 500–2500 G, feature which characteristic single-ion magnet behaviour (SIM) Co(II) them. energy barrier relaxation (Ea) 5.45–7.74 4.53–9.24 11.48–15.44 cm−1 (3). They compare well those previously reported analogous dca-bridged 2D compound [Co(dca)2(atz)2]n (4) (Ea 5.1 an field 1000 G), was subject previous report.