Structure and magnetic properties of copper(II) and cobalt(II) coordination compounds derived from optically active tridentate ligands

Trinuclear cobalt(II) and copper(II) complexes of the deprotonated N-[2-hydroxy-1(R)-methyl-2(R)-phenylethyl]-N-methylglycine (R,R(−)(H2cpse)) or N-[2-hydroxy-1(S)-methyl-2(S)-phenylethyl]-N-methylglycine (S,S(+)(H2cpse)) were prepared from the corresponding mononuclear compounds [M(Hcpse)2]·nH2O with the acetyl amino alcohol derivative. The crystal structure of the trinuclear copper(II) [Cu3(R,R(−)cpse)3(H2O)3]·8H2O (5) consists of three Cu2+ atoms with distorted square pyramidal geometry, linked by bridging oxygens from the deprotonated alcohol group to form an equilateral triangular array. This compound displays an antiferromagnetic coupling attributed to intermolecular hydrogen bonding, allowing for super-exchange pathway. The iso-structural trinuclear cobalt(II) compound [Co3(S,S(+)cpse)3(H2O)3]·7H2O (6) presents a super-paramagnetic behavior. On the other hand, a polymeric copper(II) compound {K2[Cu2(S,S(+)cpse)2(SCN)2]·H2O}n (7) was obtained from previously reported trinuclear [Cu3(S,S(+)cpse)3(H2O)3]·8H2O. This polymeric structure involves potassium ions together with the thiocyanate molecules forming a helicoidal arrangement on the c axis, presenting a ferromagnetic behavior.

Trinuclear cobalt(II) and copper(II) complexes of deprotonated chiral aminoalcohols were synthesized. The copper(II) trinuclear [Cu3(R,R(−)cpse)3(H2O)3]·8H2O (5) consists of three Cu2+ atoms in a distorted square pyramidal geometry, linked by bridging oxygen atoms to form an equilateral triangular array. It presents an antiferromagnetic coupling and a magnetic super-exchange pathway. The iso-structural trinuclear [Co3(S,S(+)cpse)3(H2O)3]·7H2O (6) complex behaves as a super-paramagnetic compound. The helicoidal polymeric {K2[Cu2(S,S(+)cpse)2(SCN)2} (7) compound presents a weak ferromagnetic behavior.Figure optionsDownload as PowerPoint slide