Control of Intramolecular Magnetic Interaction by the Spin Polarization of d? Spin to p? Orbital of an Organic Bridging Ligand

Article abstract of DOI:10.1021/j100010a046

Multinuclear metal complexes have been designed with ferromagnetic interactions between the metal centers by considering the topological network of d_? spin to the bridging ligand.The four complexes (ClO4)3*4H2O (1), (2), (NO3)4*3H2O (3), and (4), with tpa = tris(2-pyridylmethyl)amine, H3ta = trimesic acid, bpepm = 4,6-bis<(bis(2'-pyridylethyl)amino)methyl>pyrimidine, and H2bpmar = 4,6-bis<(N,N-bis(2'-pyridylmethyl)amino)methyl>-2-methylresorcinol, have been synthesized, and crystal structures of 1 and 2 have been determined.Magnetic properties have been investigated in the 2-270 K temperature range.Central metal ions in each complex are cupric for 1 and 4, high-spin ferrous for 2, and high-spin ferric species for 3, respectively.Magnetic susceptibility measurements for 1, 2, and 4 showed antiferromagnetic behavior, and the Weiss constants for the data above 100 K are -3.26, -3.86, and -2.09 K, respectively.Magnetic data for 3 have been quantitatively studied above 10 K and have revealed that 3 exhibits ferromagnetic coupling with a magnetic exchange coupling constant of J = + 0.65(3) cm^-1 (where H = -2JS₁S₂).The measurement of magnetization (M) versus the field (H) for 3 has shown that the quantum number of the total angular momentum (J) at 4.0 and 8.5 K is larger than J = 4, where the expected value (J) in absence of ferromagnetic interaction is 5/2.The ferromagnetic interaction in 3 was interpreted by the spin polarization of d_? spin to the ligand p_? orbital.Crystal data: (ClO4)3*4H2O (1), monoclinic, space group C2/c, a = 36.228(8) Angstroem, b = 19.565(3) Angstroem, c = 26.341(6) Angstroem, β = 122.07(1) deg, V = 15821(6) Angstroem³, Z = 8, R = 0.090 (R_w = 0.096) for 4992 data points with /F₀/ > 3?(F₀); (2), monoclinic, space group C2/c, a = 42.28(1) Angstroem, b = 13.467(4) Angstroem, c = 15.527(3) Angstroem, β = 94.83(2) deg, V = 8810(4) Angstroem³, Z = 8, R = 0.050 (R_w = 0.048) for 2676 data points with /F₀/ > 3?(F₀).