Plasticity in [(R_4–xR¹_x)₄N]₄[Cu₄{S₂C₂(CN)₂}₄] (x = 0–4) is Molded by a Guest Cation on an Elastic Anionic Host

Abstract

The elastic anion [Cu4(mnt)4]4– {mnt = maleonitriledithiolato, [S2C2(CN)2]2–} serves as a host to a series of guest cations [(R4–xR1x)4N]+ (R = Et, R1 = Me; x = 0–4) to form the complexes [(R4–xR1x)4N]4[Cu4{S2C2(CN)2}4]. The molecular structural design information stored in the cation is molded to the elastic anionic host‐framework through H‐bonding to create a plastic supramolecular entity. The reaction of CuCl with Na2(mnt) in a 1:1 metal/ligand ratio, followed by interaction with the respective cation, gives the cation‐dependenttetranuclear host‐guest assemblies [Me4N]4[Cu4(mnt)4] (1), [Me3EtN]4[Cu4(mnt)4] (2), [Me2Et2N]4[Cu4(mnt)4] (3), [MeEt3N]4[Cu4(mnt)4] (4) and [Et4N]4[Cu4(mnt)4] (5), which have been characterized by X‐ray structural studies in the solid state. The host cavity shrinks and expands, with varying Cu···Cu separations ranging from 2.754 to 3.952 Å, to accommodate the relevant guest ion during the crystallization process. All these complexes show identical 13C NMR and UV/Vis spectra in solution and their identical cyclic voltammetric redox behaviors also imply the presence of a common entity. The ESI mass spectra in acetonitrile confirm the presence of this common {Cu4(mnt)4} core. The elastic {Cu4(mnt)4} core participates in extensive hydrogen bonds in the presence of different quaternary cations in solution during the crystallization process and the cation determines the final shape of the anion in the solid state. Depending on the length and nature (symmetric or non‐symmetric) of the alkyl groups attached to the quaternary cation, the overall geometry of the anion assumes different degrees of openness in a partially opened umbrella shape. The {Cu4(mnt)4} moiety is cleaved by treatment with PPh3 to give a monomer, which has been isolated as [Et4N][Cu(mnt)PPh3] (6).(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Native Protein Template Assisted Synthesis of Non-Native Metal-Sulfur Clusters

“…Furthermore, unlike covalent assembly, non-covalent (supramolecular) assembly can allow the entry and exit of the guest molecule in the host cavity reversibly. The designed information of molecular structure is stored in the host-cavity (protein template) that builds the guest structure through non-covalent interactions, including hydrogen-bonding, ion-pair, and hydrophobic interactions [42,43]. Inspired by Nature, the non-native metal ions have been recruited into protein scaffolds by non-covalent or covalent chemical ways to design artificial metalloenzymes.…”

Oxidation of phosphine by sulfur or selenium involving a catalytic cycle in the interconversion of monomer and tetramer forms of copper-maleonitriledithiolate complexes

“…An outstanding common structural feature in [Cu 8 (i-mnt) 6 ] 4-, [Cu 8 (dts) 12 ] 4-, and [Cu 8 (mnt) 6 ] 4-clusters 4,5 is the similarity of cubic structure where all the coordinated sulfurs are attached as µ 2 -S bridging mode. Recently, we have reported the trinuclear, [Cu 3 (mnt) 3 ] 4-and tetranuclear, [Cu 4 (mnt) 4 ] 4-complexes 6,7 where the coordinated sulfurs vary their attachment in µ 1 -S and µ 2 -S bridging modes with their interconversion leading to octanuclear complex.…”

Oxygen Activation by a Copper Complex with Sulfur-Only Coordination Relevant to the Formylglycine Generating Enzyme

“…[Et 4 N] 4 [Cu 4 (mnt) 4 ] (1) was synthesized according to the literature procedure. 9 UV−vis spectra were recorded on a Lambda 35 UV−vis spectrometer (PerkinElmer). Infrared spectra were recorded on a PerkinElmer Spectrum 100 FT-IR Spectrophotometer with pressed KBr disks.…”

“…These distances are comparable to the values reported for other Cu I complexes. 9,29 The copper atom in complex 2 is lying in the same plane as the three-sulfur basal plane (Cu1−S3 plane: 0.038 Å), whereas the copper atoms in complex 3 are displaced by 0.143 (Cu1) and 0.127 Å (Cu2) from the three-sulfur basal plane in a distorted trigonal planar geometry. The Cu•••Cu distance of 2.7341(8) Å in complex 3 is less than the sum of van der Waals radii of two copper atoms (2.80 Å) 30 which indicates that the complex is stabilized by significant cuprophilic interaction.…”

“…Complexes 2 and 3 show quasi-reversible peaks at E 1/2 = 0.32 and 0.24 V vs Ag/AgCl in dichloromethane, which are assignable to Cu I /Cu II couples for 2 and 3, respectively (Figure 5). 9,33 The peaks at E 1/2 = −0.73 and −0.78 V presumably arise due to the coordinated mnt ligand. 34 An additional peak at E pa = −0.10 V for 2 might be due to the oxidation of the terminal hydrosulfide ligand.…”