Dinuclear, tetranuclear and one-dimensional pyrazine-based copper(ii) complexes: preparation, X-ray structure and magnetic properties

Abstract

The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(2)(tppz)(H(2)O)(2)(CF(3)SO(3))(4)] (1), [Cu(tppz)(CrO(4))](n) x 3nH(2)O (2) and [Cu(4)(tppz)(4)(H(2)O)(4)(MoO(4))(2)](CF(3)SO(3))(4) x 7 H(2)O (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complex 1 is a dinuclear species where tppz adopts a bis-tridentate bridging mode with an intramolecular copper-copper separation of 6.5221(6) A. Each copper(II) ion in 1 has an elongated octahedral geometry with three tppz nitrogen atoms and a water molecule in the equatorial positions and two triflate oxygen atoms occupying the axial sites. Complex 2 is a uniform copper(II) chain where the copper atoms are bridged by two oxygen atoms of the chromate group (mu(1,2)-CrO(4)), the value of the intrachain metal-metal separation being 4.2614(5) A. Each copper(II) ion in 2 exhibits a somewhat distorted square pyramidal geometry with three nitrogen atoms from a tridentate tppz ligand and a chromate oxygen atom in the basal plane and an oxygen atom of a symmetry-related chromate group in the apical position. Complex 3 is a cyclic tetranuclear compound where peripheral [Cu(tppz)(H(2)O)](2+) units are connected through two molybdate groups, each one adopting the mu(1,1,2)-MoO(4) bridging mode. Regular alternating five [Cu(1) and Cu(4)] and six [Cu(2) and Cu(3)] coordinated copper(II) ions occur in 3 with distorted square pyramidal CuN(3)O(2) and elongated octahedral CuN(3)O(3) surroundings, respectively. The four copper atoms in 3 have in common the presence of a molybdate-oxygen and three tppz-nitrogen atoms in the basal [Cu(1) and Cu(4)]/equatorial [Cu(2) and Cu(3)] planes and a water molecule in the apical [Cu(1) and Cu(4)]/one axial [Cu(2) and Cu(3)] positions whereas the remaining axial position is occupied by a molybdate-oxygen [Cu(2) and Cu(3)]. The shorter intramolecular copper-copper separation is 3.371(1) A [Cu(2)...Cu(3)], the other ones varying in the range 5.537(1)-6.301(1) A. The investigation of the magnetic properties of 1-3 in the temperature range 1.9-295 K has shown the occurrence of intermediate antiferro- [J = -48.0(1) cm(-1) with H = -JS(1) x S(2) (1)], weak ferro- [J = +0.28(1) cm(-1) with H = -JSigma(i)S(i) x S(i+I) (2)] and coexistence of weak ferro- and antiferromagnetic interactions [J(1) = +2.38(2) cm(-1), J(2) = +0.56(2) cm(-1) and J(3) = -1.53(2) cm(-1) with H = -J(1) (S(2) x S(3)) + J(2) (S(1) x S(3) + S(2) x S(4)) + J(3) (S(1) x S(2) + S(3) x S(4)) (3)] between the copper(II) ions across bis-tridentate tppz (1), mu(1,2)-CrO(4) (2), di-mu(1,1)-MoO(4) and mu(1,2)-MoO(4) (3) bridges. The values of the magnetic interactions are analyzed in terms of simple orbital symmetry considerations and compared with those reported for parent systems.

Cyclometalated Ruthenium, Osmium, and Iridium Complexes Bridged by an NCN–Pyrene–NCN Derivative – Synthesis and Comparison of Optical, Thermal, and Electrochemical Properties

“…Dinuclear metal complexes containing bridging ligands have been the subject of recent research investigations Complexes containing ruthenium, osmium, rhodium, nickel, copper, and iron have been described, and the bridges are mainly 2,3,5,6‐tetrasubstituted pyrazine ligands. The use of cyclometalating pyrene derivatives is insufficiently studied, and only complexes with ruthenium have been described .…”

Crystal structure of diaquabis(μ-4-hydroxyphthalato-κ2O,O')- bis(1,10-phenanthroline-κ2N,N')dicopper(II) pentahydrate, [Cu(H2O)(C12H8N2)(C8H4O5)]2 · 5H2O

“…Metal-organich ybrid materials containing paramagnetic metal ions have attracted intense interest for their fascinating structural diversities and functional applications in the fields of molecular magnetism and material chemistry [2][3][4]. In aspontaneous assembly process, the structural information stored in the organic ligands is read by the metal ion according to their coordination tendency.…”

Structurally Diverse Polynuclear Copper(I) Complexes Bridged by Pyrimidine–, Pyrazine–, and Triazine–based Ligands with Several 2–Pyridyl Groups

“…In contrast, coordination mode (iv–c) is a relatively common coordination form. For instance, mononuclear tppz complexes of Mn(II), Fe(II), Ni(II), Co(II), Cu(II), Zn(II), Ru(II), Ru(III), Rh(III), Re(II), and Ir(III) have been widely reported in coordination mode (iv–c), together with dinuclear tppz complexes of Mn(II), Cu(II), and polymeric tppz complexes of Mn(II), Co(II), Co(II)/V m O n , Ni(II), Ni(II)/V m O n , Cu(II), Cu(II)/V m O n , Zn(II), and Cd(II) containing coordination mode (iv–c). Regarding tppz complexes in bimetallic coordination modes (iv–d) – (iv–g), coordination mode (iv–g) is a most popular coordination manner than coordination modes (iv–d) – (iv–f).…”

“…Regarding tppz complexes in bimetallic coordination modes (iv–d) – (iv–g), coordination mode (iv–g) is a most popular coordination manner than coordination modes (iv–d) – (iv–f). For instance, dinuclear tppz complexes of Ni(II), Cu(II), Zn(II), Ru(II), Ru(I)/Ru(II), Ru(II)/Ru(III), Ru(I)/Pt(II), Pd(II), Cd(II), and Pt(II) have been widely reported in coordination mode (iv–g). Furthermore, a few trinuclear tppz complexes of Ni(II) and Ru(I)/Pt(II), as well as tetranuclear tppz complexes of Cu(II), Zn(II), and Rh(I) containing coordination mode (iv–g), have also been reported, together with diverse polymeric tppz complexes of Co(II), Co(II)/Mo m O n , Ni(II), Ni(II)/Mo m O n , Cu(II), Cu(II)/V x F y O z , Cu(II)/Mo m O n , Zn(II)/V m O n , and Cd(II) containing coordination mode (iv–g).…”