Syntheses, Structural Analyses, and Magneto-Structural Correlations of Three Polymeric Fe(II) Complexes with Azide Ligand

Abstract

Three new metal-organic polymeric complexes, [Fe(N(3))(2)(bpp)(2)] (1), [Fe(N(3))(2)(bpe)] (2), and [Fe(N(3))(2)(phen)] (3) [bpp = (1,3-bis(4-pyridyl)-propane), bpe = (1,2-bis(4-pyridyl)-ethane), phen = 1,10-phenanthroline], have been synthesized and characterized by single-crystal X-ray diffraction studies and low-temperature magnetic measurements in the range 300-2 K. Complexes 1 and 2 crystallize in the monoclinic system, space group C2/c, with the following cell parameters: a = 19.355(4) A, b = 7.076(2) A, c = 22.549(4) A, beta = 119.50(3) degrees, Z = 4, and a = 10.007(14) A, b = 13.789(18) A, c = 10.377(14) A, beta = 103.50(1) degrees, Z = 4, respectively. Complex 3 crystallizes in the triclinic system, space group P(-)1, with a = 7.155(12) A, b = 10.066(14) A, c = 10.508(14) A, alpha = 109.57(1) degrees, beta = 104.57(1) degrees, gamma = 105.10(1) degrees, and Z = 2. All coordination polymers exhibit octahedral Fe(II) nodes. The structural determination of 1 reveals a parallel interpenetrated structure of 2D layers of (4,4) topology, formed by Fe(II) nodes linked through bpp ligands, while mono-coordinated azide anions are pendant from the corrugated sheet. Complex 2 has a 2D arrangement constructed through 1D double end-to-end azide bridged iron(II) chains interconnected through bpe ligands. Complex 3 shows a polymeric arrangement where the metal ions are interlinked through pairs of end-on and end-to-end azide ligands exhibiting a zigzag arrangement of metals (Fe-Fe-Fe angle of 111.18 degrees) and an intermetallic separation of 3.347 A (through the EO azide) and of 5.229 A (EE azide). Variable-temperature magnetic susceptibility data suggest that there is no magnetic interaction between the metal centers in 1, whereas in 2 there is an antiferromagnetic interaction through the end-to-end azide bridge. Complex 3 shows ferro- as well as anti-ferromagnetic interactions between the metal centers generated through the alternating end-on and end-to-end azide bridges. Complex 1 has been modeled using the D parameter (considering distorted octahedral Fe(II) geometry and with any possible J value equal to zero) and complex 2 has been modeled as a one-dimensional system with classical and/or quantum spin where we have used two possible full diagonalization processes: without and with the D parameter, considering the important distortions of the Fe(II) ions. For complex 3, the alternating coupling model impedes a mathematical solution for the modeling as classical spins. With quantum spin, the modeling has been made as in 2.

Expanding the 2,2′-bipyrimidine bridged 1D homonuclear coordination polymers family: [MII(bpym)Cl2] (M = Fe, Co) magnetic and structural characterization

“…The obtained value for the exchange coupling constant is in good agreement with previous reported Fe(II) bpym bridged examples. 8,9,13,14 For compound 2 fitting of the magnetic data (Fig. 3) was employed down to 15 K. The sharp increase in χ m below this temperature is probably related to cooperative effects.…”

A Family of Enneanuclear Iron(II) Single‐Molecule Magnets

“…They include discrete dinuclear or tetranuclear m 1,1 -azido-or cyanato-bridged species, [20] a 2D m 1,1 -N 3 -bridged layered complex, [27] and 2D (m 1,3 -N 3 ) or 1D (m 1,1 -N 3 and m 1,3 -N 3 ) coordination polymers. [28] Thus, complexes 2 and 3 are the first two examples of the m 1,1,1,1 bridging mode in iron(II) chemistry.…”

A dinuclear copper(II) complex and a zigzag chain iron(II) polymer based on the 4-antipyrine derived Schiff base ligands: The hydroxylation and redox occurred under the solvothermal conditions

“…Symmetry code: (i) 1 2 þ x; 1 2 À y; 1 2 þ z. indicative of no magnetic interaction. The low temperature data shows significant zero-field splitting of the single iron(II) ion ground-state [24]. In summary, a new dinuclear copper(II) compound, [Cu 2 (L1-O) 2 ] (1) and a zigzag chain polymer, {[FeCl 2 (L2)]} n (2) have been synthesized by solvothermal reactions and structurally characterized.…”