Pseudohalide‐Controlled Assemblies of Copper–Schiff Base Complexes with an Encapsulated Sodium Ion: Synthesis, Crystal Structure, and Computational Studies

Abstract

Three new hetero-bimetallic coordination complexes [Na-(CuIIL1)2](ClO4)·0.5H2O (1), [Na(CuIIL2)2][CuI2(μ1,3-NCS)3]n\ud (2), and {[Na(CuIIL3)2](μ1,5-dca)}n (3; dca = dicyanamide) have been synthesized by using different Schiff base ligands [e.g., L1H2 = N,N=-bis(3-methoxysalicylidenimino)-1,3-diaminopentane, L2H2 = N,N=-bis(3-ethoxysalicylidenimino)- 1,3-diaminopropane, and L3H2 = N,N=-bis(5-bromo-3-methoxysalicylidenimino)-1,3-diaminopropane] in the presence\ud of pseudohalide coligands N3–, SCN–, and N(CN)2– (dca),respectively. The ligands and the complexes have been characterized\ud by microanalytical and spectroscopic techniques. The structures of the complexes, determined by single-crystal X-ray diffraction studies, show that in all cases a trinu-clear Na(CuIIL)2 unit is formed, but of different configurations. 1 does not include N3– anions. In contrast, in 2, SCN– extrudes partial in situ reduction of CuII to lead to the formation of an infinite [CuI\ud 2(μ1,3-NCS)3]n anionic chain; and in 3, N(CN)2– bridges the metal–ligand assemblies to form a 1D polymeric chain. ESI-MS, UV/Vis spectroscopy, and cyclic voltammetry were performed to investigate the solution-state behavior of the complexes. Theoretical calculations of the optimized geometries of the complexes were carried out at the BLYP/DNP level to determine their relative stabilities from the HOMO–LUMO gap and chemical softness values

Novel mixed-valence Cu compounds formed by Cuii dimers with double oximato bridges: in situ formation of anionic layer [Cu2(SCN)3]nn−

“…3495 cm −1 , attributable to ν s (O-H) vibrations of the coordinated water molecules, and a characteristic double band of the perchlorate anion at 1088-1118 cm −1 . 36 The intense doublets at 2130 and 2045 cm −1 in the spectra of 2 and 3, respectively, confirm the presence of the bridging thiocyanate groups. 36 Variable temperature magnetic susceptibility measurements…”

“…36 The intense doublets at 2130 and 2045 cm −1 in the spectra of 2 and 3, respectively, confirm the presence of the bridging thiocyanate groups. 36 Variable temperature magnetic susceptibility measurements…”

“…These display strong and sharp absorption bands at 1644, 1639 and 1627 cm −1 , in 1-3, respectively, that can be assigned to the >CvN stretching frequency of the coordinated Schiff base ligands HL 1 and HL 2 . 35 The coordination of the ligand to the metal center is substantiated by a band appearing at 462, 464 and 469 cm −1 for 1-3, respectively, mainly attributed to the Cu-N stretching, 36 while bands at 1141, 1137 and 1176 cm −1 suggest the presence of N-O bonds. 32 Complex 1 exhibits a strong and broad band at ca.…”

Unexplored analytics of some novel 3d–4f heterometallic Schiff base complexes

“…The spectrum of the free ligand exhibits two inter ligand charge-transfer (CT) bands with l max 227 nm which can be attributed to p-p* transition. 32 The l max of 261 nm is attributed to n-p* transition. The Cu(L 2À )$CH 3 OH complex also shows a peak at 225 nm for p-p* transition and the other two distinct peaks at 280 and 360 nm are observed for n-p* and LMCT transitions.…”

[RuIII(valen)(CN)2]−: a New Building Block To Design 4d–4f Heterometallic Complexes

“…The K ion is located in the open compartment, being coordinated by two phenoxo bridging O atoms and by two aqua ligands. Coordination of the K ion by the O atoms from the open compartment of the valen ligand is not surprising because the O 2 O′ 2 cavity has a marked crown ether-like ability to encapsulate alkali-metal ions . The K–O distances vary between 2.676(7) and 2.795(8) Å. Interestingly, analysis of the packing diagram for 1 reveals the formation of supramolecular dimers, {[K­(H 2 O) 2 Ru III (valen)­(CN) 2 ]} 2 , through anagostic interactions established between one H atom belonging to a CH 3 group from one [KRu] dimer and the K ion from another one (Figure ).…”