The Goldilocks principle in action: synthesis and structural characterization of a novel {Cu4(μ3-OH)4} cubane stabilized by monodentate ligands

Abstract

A {Cu4(μ3-OH)4} compound, where four copper(II) and four μ3-bridging oxygen atoms occupy alternate corners of a slightly distorted cube, has been prepared and structurally characterized. This species, formulated as [Cu4(μ3-OH)4(Htmpz)8](ClO4)4·1.5Et2O (Htmpz = 3,4,5-1H-trimethyl pyrazole), can be classified as belonging to type I Cu4O4 cubane complexes, and is better described as two Cu(II)-(μ-OH)2-Cu(II) units held together by four long Cu-O bonds. The central distorted cubane core is stabilized by neutral monodentate ligands (Htmpz) and perchlorate anions, as demonstrated by single-crystal X-ray structure analysis. The title compound was obtained by hydrolysis of a dinuclear methoxo-bridged species, [Cu(μ-OCH3)(Htmpz)2]2(ClO4)2, which was prepared by reaction of [Cu(Htmpz)4(ClO4)2] with methanol. All these reactions represent a nice example of the Goldilocks principle in action in coordination chemistry, since each single actor (solvent, counteranion, and ligand) has the "just right" electronic, steric or coordinative properties which determine the fate of the final products.

Tuning the Fluorescence Emission and HOMO‐LUMO Band Gap in Homoleptic Zinc(II) Complexes with N,O‐Bidentate (Imidazo[1,5‐a]pyrid‐3‐yl)phenols

“…Among nitrogen‐based ligands, imidazo‐pyridines are known for their interesting photochemical properties, both as free molecules and when coordinated to transition metals . In our ongoing study on complexes with nitrogen‐containing ligands, we also investigated zinc(II), and silver(I) complexes bearing N , N ‐coordinated imidazo‐pyridines. Herein, we report on the luminescence properties of a series of homoleptic zinc(II) complexes (Zn(L R ) 2 ) with (imidazo[1,5‐ a ]pyrid‐3‐yl)phenols, which in this case act as N , O ‐bidentate ligands.…”

Synthesis, Structure, and Photophysical Properties of Blue‐Emitting Zinc(II) Complexes with 3‐Aryl‐Substituted 1‐Pyridylimidazo[1,5‐a]pyridine Ligands

“…In the past, we widely explored the coordination chemistry of N‐based multidentate ligands18 and paid special attention to pyrazole and its analogues (imidazole and triazole) both in their neutral19 and anionic azolate forms 20. The corresponding transition‐metal complexes have found applications in catalysis, materials science, and in the synthesis of polynuclear systems.…”

Selective Recognition of Ammonium over Potassium Ion with Acyclic Receptor Molecules Bearing 3,4,5-Trialkylpyrazolyl Groups

“…25 and 26 (see also ref. 27 ). In addition to the purification methods described there, a dichloromethane solution of the crude reaction product was treated with a NaOH solution (2-5 %).…”