Copper(II) Carboxylate Dimers Prepared from Ligands Designed to Form a Robust π···π Stacking Synthon: Supramolecular Structures and Molecular Properties

Abstract

The reactions of bifunctional carboxylate ligands (1,8-naphthalimido)propanoate, (L(C2)(-)), (1,8-naphthalimido)ethanoate, (L(C1)(-)), and (1,8-naphthalimido)benzoate, (L(C4)(-)) with Cu(2)(O(2)CCH(3))(4)(H(2)O)(2) in methanol or ethanol at room temperature lead to the formation of novel dimeric [Cu(2)(L(C2))(4)(MeOH)(2)] (1), [Cu(2)(L(C1))(4)(MeOH)(2)]·2(CH(2)Cl(2)) (2), [Cu(2)(L(C4))(4)(EtOH)(2)]·2(CH(2)Cl(2)) (3) complexes. When the reaction of L(C1)(-) with Cu(2)(O(2)CCH(3))(4)(H(2)O)(2) was carried out at -20 °C in the presence of pyridine, [Cu(2)(L(C1))(4)(py)(4)]·2(CH(2)Cl(2)) (4) was produced. At the core of complexes 1-3 lies the square Cu(2)(O(2)CR)(4) "paddlewheel" secondary building unit, where the two copper centers have a nearly square pyramidal geometry with methanol or ethanol occupying the axial coordination sites. Complex 4 contains a different type of dimeric core generated by two κ(1)-bridging carboxylate ligands. Additionally, two terminal carboxylates and four trans situated pyridine molecules complete the coordination environment of the five-coordinate copper(II) centers. In all four compounds, robust π···π stacking interactions of the naphthalimide rings organize the dimeric units into two-dimensional sheets. These two-dimensional networks are organized into a three-dimensional architecture by two different noncovalent interactions: strong π···π stacking of the naphthalimide rings (also the pyridine rings for 4) in 1, 3, and 4, and intermolecular hydrogen bonding of the coordinated methanol or ethanol molecules in 1-3. Magnetic measurements show that the copper ions in the paddlewheel complexes 1-3 are strongly antiferromagnetically coupled with -J values ranging from 255 to 325 cm(-1), whereas the copper ions in 4 are only weakly antiferromagnetically coupled. Typical values of the zero-field splitting parameter D were found from EPR studies of 1-3and the related known complexes [Cu(2)(L(C2))(4)(py)(2)]·2(CH(2)Cl(2))·(CH(3)OH), [Cu(2)(L(C3))(4)(py)(2)]·2(CH(2)Cl(2)) and [Cu(2)(L(C3))(4)(bipy)]·(CH(3)OH)(2)·(CH(2)Cl(2))(3.37) (L(C3)(-) = (1,8-naphthalimido)butanoate)), while its abnormal magnitude in [Cu(2)(L(C2))(4)(bipy)] was qualitatively rationalized by structural analysis and DFT calculations.

Synthesis, crystal structure and EPR spectroscopic analysis of novel copper complexes formed from N-pyridyl-4-nitro-1,8-naphthalimide ligands

“…[1][2][3][4] More recently naphthalimide derivatives have been utilised as building blocks in metal based supramolecular architectures where their π-deficient nature and ability to be readily functionalised has been exploited giving rise to systems in which the extension of the structure occurs through π-based interactions. This work has largely been pioneered by Reger and co-workers who, over the last decade, have functionalized the 1,8-naphthalimide moiety at the imide nitrogen site, with various transition metal ion coordinating functional groups such as carboxylates, [5][6][7][8][9][10][11][12][13][14] pyrazoles [15][16][17][18][19] and other coordinating groups, 20 and studied the structural aspects of the resulting complexes.…”

Protonation effect on ligands in EuL: a luminescent switcher for fast naked-eye detection of HCl

“…interplanar angles of 0°, interplanar perpendicular distance of 3.44 Å and interplanar slippage of 1.82 Å), we may conclude that the quinoline π−π stacking interactions between adjacent tweezer-type SBUs are considerably strong. 21,22 Every two rods are coupled by π−π stacking interactions between the interdigitated aromatic rings of tweezer-type SBUs, resulting in 2D layer framework ( Figure 1c). Viewed down the crystallographic c axis, each rod connects four adjacent rods to generate "squares" through tweezer-type SBUs by π−π stacking interactions (Figure 1d), and results in a threedimensional supramolecular structure.…”

Rare Supramolecular Assemblies of a Dicopper(II)‐tetracarboxylate Stabilized by (Methanol)6, Dimethyl Sulfoxide and 4,4′‐Azobipyridyl Bridges

“…Copper(II) carboxylates have gained increasing attention due to considerable interest in structural chemistry, gas storage, magnetism, catalysis, and biology . They are known to form a variety of structures depending on the nature of ligand, solvent and reaction conditions.…”