Synthesis of the first heterometalic star-shaped oxido-bridged MnCu₃complex and its conversion into trinuclear species modulated by pseudohalides (N₃⁻, NCS⁻and NCO⁻): Structural analyses and magnetic properties

Abstract

A tetra-nuclear, star-shaped hetero-metallic copper(II)-manganese(II) complex, [{CuL(H(2)O)}(2)(CuL)Mn](ClO(4))(2) (1) has been synthesized by reacting the "complex as ligand" [CuL] with Mn(ClO(4))(2) where H(2)L is the tetradentate di-Schiff base derived from 1,3-propanediamine and 2-hydroxyacetophenone. Upon treatment with the polyatomic anions azide, cyanate, or thiocyanate in methanol medium, complex 1 transforms into the corresponding trinuclear species [(CuL)(2)Mn(N(3))(2)] (2), [(CuL)(2)Mn(NCO)(2)] (3) and [(CuL)(2)Mn(NCS)(2)] (4). All four complexes have been structurally and magnetically characterized. In complex 1 the central Mn(II) ion is encapsulated by three terminal [CuL] units through the formation of double phenoxido bridges between Mn(II) and each Cu(II). In complexes 2-4 one of the CuL units is replaced by a couple of terminal azide, N-bonded cyanate or N-bonded thiocyanate ions respectively and the central Mn(II) ion is connected to two terminal Cu(II) ions through a double asymmetric phenoxido bridge. Variable temperature magnetic susceptibility measurements show the presence of moderate ferrimagnetic exchange interactions in all the cases mediated through the double phenoxido bridges with J values (H = -JS(i)S(i + 1)) of -41.2, -39.8 and -12.6 cm(-1) (or -40.5 and -12.7 cm(-1) if we use a model with two different exchange coupling constants) for the tetranuclear MnCu(3) cluster in compound 1 and -20.0, -17.3 and -32.5 cm(-1) for the symmetric trinuclear MnCu(2) compounds 2-4. These ferrimagnetic interactions lead to spin ground states of 1 (5/2 - 3*1/2) for compound 1 and 3/2 (5/2 - 2*1/2) for compounds 2-4.

Trinuclear complexes of [CuL] (H2L = N,N′-bis(salicylidene)-1,4-butanediamine) with HgX2 (X−= N3− and NCO−): Facile crystallization with Z′ = 1 and Z′ = 0.5 for both complexes

“…In case of compounds 2 and 2 0 , the intense peak at 2170 and 2169 cm À1 (Figs. S3 and S4), respectively also confirm the formation of trinuclear adduct with cyanate as a coligand [29]. In the spectra of all these compounds a strong and sharp band around 1620 cm À1 were found due to the azomethane m(C@N) group of the Schiff base [30].…”

Key Role of Size and Electronic Configuration on the Sign and Strength of the Magnetic Coupling in a Series of Cu2Ln Trimers (Ln = Ce, Gd, Tb, Dy and Er)

“…These studies established that the α-methylation on the N 2 O 2 donor Schiff base ligand has a key role in determining the structures of the resulting compounds [40][41][42][43][44][45][46]. However, such studies have not been performed with lanthanide-containing trinuclear coordination clusters for these complexes.…”

Use of Cu(II)-di-Schiff bases as metalloligands in the formation of complexes with Cu(II), Ni(II) and Zn(II) perchlorate

“…Using Cu(II) complexes of salen type di-Schiff bases as metalloligands, six examples of single atom oxido bridged star-shaped tetra-nuclear complexes have been reported. These examples include three with M = Na + [20,44,45], one with M = K + [46] and one for each with Cd 2+ [17] and Mn 2+ [21]. Four of these complexes are constituted by the ''metalloligands'' [CuL 2 ] and other two by aother metalloligand [Cu(acacen)] (where [acacen] 2À = N,N 0 -ethylenebis(acety1acetoniminato)).…”

“…results in a bent structure. On the other hand, when the counter anions are non-coordinating or weakly coordinating such as perchlorate, three ''metalloligands'' can coordinate to a central metal ion to result in rather unusual star-shaped tetranuclear complexes [17,20,21]. However, trinuclear complexes with such anions are limited and hence no generalization on the shape of the trinuclear molecules could be done.…”

“…Among the divalent first transition elements, Cu(II) forms the most stable complexes with these Schiff bases [10][11][12][13] and therefore, these neutral Cu-chelates have been used frequently to form complex with another metal ions. In most of these complexes, the oxygen atoms of two ''metalloligands'' coordinate to a second ion to result in trinuclear complexes [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. These trinuclear complexes can be homonuclear i.e.…”