Aggregation of [Cu${{\bf }{{{\bf II}\hfill \atop \bf 4\hfill}}}$] Building Blocks into [Cu${{\bf }{{{\bf II}\hfill \atop \bf 8\hfill}}}$] Clusters or a [Cu${{\bf }{{{\bf II}\hfill \atop \bf 4\hfill}}}$]_∞ Chain through Subtle Chemical Control

Abstract

Coordination complexes of the ligand H3L [1,3-bis(3-oxo-3-phenylpropionyl)-2-hydroxy-5-methylbenzene] with Cu(II) are reported. Clusters showing various nuclearities or modes of supramolecular organization have been prepared by slightly changing the reaction conditions and have been crystallographically characterized. The reaction of H3L with one equivalent of Cu(OAc)2 in DMF yields the dinuclear complex [Cu2(HL)2(dmf)2] (1). Reaction in MeOH of H3L with an increased amount of metal, in the form of Cu(NO3)2, and excess strong base (nBu4NOH) affords the cluster [Cu8(L)2(OMe)8(NO3)2] (2). Complex 2 is a dimer of two linear [Cu4] arrays bridged by methoxide ligands, where the polynucleating ligand is fully deprotonated. The [Cu4]2 clusters are linked to each other by NO3- bridges to form one-dimensional coordination polymers. The link between [Cu8] units and their relative spatial positioning can be modified by changing the anion of the Cu(II) salt, as demonstrated by the synthesis of the cluster polymers [Cu8(L)2(OMe)8Cl2] (3) and [Cu8(L)(OMe)7.86Br2.14] (4), where only NO3- has been replaced by Cl- or Br-, respectively. Similarly, when ClO4- is used, compound [Cu8(L)2(OMe)8(ClO4)2(MeOH)4] (5) can be isolated. It contains independent [Cu8] units. A slight change in the stoichiometry of the reaction leading to 2 affords the related complex catena-[Cu4(L)(OMe)3(NO3)2(H2O)0.36] (6). This polymer contains essentially the same [Cu4] moiety as 2, albeit organized in a completely different arrangement. Each [Cu4] unit in 6 is linked by OMe- ligands to two such equivalent groups to form an infinite chain. Magnetic susceptibility measurements reveal weak antiferromagnetic exchange between Cu(II) centers in 1 (J = -0.73 cm(-1)) and strong antiferromagnetic coupling within [Cu4] chains in 2, 5, and 6 (most negative J values of -113.8 and -177.3 cm(-1) for 2 and 6, respectively).

Structure and magnetism of a porous three-dimensional metal-organic framework based on planar tetranuclear copper(II) cluster units

“…The value of  M T at 280 K is 1.58 cm 3 K mol 1 , which is near to that expected for four magnetically isolated copper(II) S = 1 / 2 indicates that a small amount of a paramagnetic impurity exists (this is very common in this type of system, and is especially apparent with strongly antiferromagnetic compounds) [30]). …”

Designed Topology and Site‐Selective Metal Composition in Tetranuclear [MM′⋅⋅⋅M′M] Linear Complexes

“…[16,17] In some cases, the aggregation of M 4 chains have produced other architectures, such as [M 4 ] 2 dimers [18] or [M 4 ] n polymers. [19] The use of b-diketone groups as part of ligands has been used also by other groups for the assembly of a variety of coordination complexes. [20][21][22][23][24] We have recently directed our attention towards ligands capable of keeping metals separate into two semi-independent groups within a molecule, since these types of assemblies have been proposed as good candidates to become two-qbit quantum gates for quantum computing.…”

A Zig‐Zag [MnII4] Cluster from a Novel Bis(β‐diketonate) Ligand

“…Maximum occupancy of their coordination pockets would result in tetranuclear clusters in form of [M 4 ] chains [17] for H 3 L1 and aligned [M 2 ] 2 dimers of dimers for H 4 L2. Reactions of the latter with M(OAc) 2 salts have resulted invariably in the formation of complexes of the type [M 2 (H 2 L2) 2 (S) n ] (n = 2 or 4; S = solvent; M = Mn, Ni, Co, Cu).…”

“…[14] We have been interested in preparing new ligands incorporating various β-diketone units and other donor groups in a linear fashion (H 3 L1 and H 4 L2 in [ Scheme 1), [15,16] aimed at forming molecular strings of metal ions in close proximity. Maximum occupancy of their coordination pockets would result in tetranuclear clusters in form of [M 4 ] chains [17] for H 3 L1 and aligned [M 2 ] 2 dimers of dimers for H 4 L2. Reactions of the latter with M(OAc) 2 salts have resulted invariably in the formation of complexes of the type [M 2 (H 2 L2) 2 (S) n ] (n = 2 or 4; S = solvent; M = Mn, Ni, Co, Cu).…”