Linkage Isomerism in Coordination Polymers

Abstract

The use of the recently prepared polynitrile ligand tcnopr3OH(-) ([(NC)(2)CC(OCH(2)CH(2)CH(2)OH)C(CN)(2)](-)) with different salts of Fe(II), Co(II), and Ni(II) has led to a very rare example of linkage isomerism in a coordination chain. These pairs of linkage isomers can be formulated as [M(tcnopr3OH-κN,κO)(2)(H(2)O)(2)]; M = Fe (1), Co (3), and Ni(5) and [M(tcnopr3OH-κN,κN')(2)(H(2)O)(2)]; M = Fe (2), Co (4), and Ni (6). Compounds 1-2, 3-4, and 5-6 are three pairs of linkage isomers since they present the same formula and chain structure and they only differ in the connectivity of the polynitrile ligand bridging the metal ions in the chain: through a N and an O atom (1κN:2κO-isomer) or through two N atoms (1κN:2κN'-isomer). The magnetic properties show, as expected, very similar behaviors for both isomers.

Polynitrile anions as ligands: From magnetic polymeric architectures to spin crossover materials

“…As a consequence of this multiple coordinating modes, this ligand has afforded two different series of compounds with the same formula when combined with the first row transition metals. Furthermore, in the case of the Fe(II) derivative, this ligand has given rise to a couple of linkage isomers in a chain compound which is, as far as we know, the first example of linkage isomerism in a chain compound [24]. When combined with Mn(II), Fe(II) and Cu (II) (20) and Ni(II) (21) [20].…”

“…The 4,4 -bpy ligand has been only very recently be used as coligand with two polynitrile anions: tcnoetOH − [29] and tcnopr3OH [30]. In the first case the 4,4 -bpy and tcnoetOH − ligands have afforded three isostructural compounds that can be formulated as [M(tcnoetOH) 2 (4,4 -bpy)(H 2 O) 2 ] with M = Fe(II) (27), Co(II) (28) and Ni(II) (29) [29].…”

“…In the first case the 4,4 -bpy and tcnoetOH − ligands have afforded three isostructural compounds that can be formulated as [M(tcnoetOH) 2 (4,4 -bpy)(H 2 O) 2 ] with M = Fe(II) (27), Co(II) (28) and Ni(II) (29) [29]. This series of compounds presents a chain structure formed by bridging 4,4 -bpy where the metal atoms are coordinated by two trans 4,4 -bpy, two trans tcnoetOH − ligands and two trans water molecules to form a centro-symmetric octahedral MN 4 O 2 coordination geometry (Fig.…”

A Spin Crossover Transition in a Mn(II) Chain Compound

“…Thus, Fe(II) forms a centro-symmetric monomer formulated as [Fe II Among the polynitrile ligands used to prepare coordination polymers (Scheme 1), the most versatile one has been tcnopr3OH´(1,1,3,3-tetracyano-2-(3-hydroxypropoxy)-propenide), thanks to the presence of a longer and, therefore, more flexible alkyl chain. Thus, the combination of this ligand with different transition metals yielded two closely-related series of CP, formulated as [M(1kN:2kO-tcnopr3OH) 2 [22,28]. Interestingly, three metal ions (Fe, Co and Ni) gave rise to both linkage isomers and constitute the first series of CP presenting linkage isomerism [28].…”

“…Thus, the combination of this ligand with different transition metals yielded two closely-related series of CP, formulated as [M(1kN:2kO-tcnopr3OH) 2 [22,28]. Interestingly, three metal ions (Fe, Co and Ni) gave rise to both linkage isomers and constitute the first series of CP presenting linkage isomerism [28].…”