Heterometallic Mixed-Valence Copper(I,II) Cyanides that were Tuned by Using the Chelate Effect: Discovery of Famous Cairo Pentagonal Tiling and Unprecedented (3,4)-Connected {83}2{86} Topological 3D Net

• Published in: Chemistry, an Asian journal Vol. 8; no. 7; pp. 1587 - 1595
• Main Authors: Qin, Ying-Lian, Yao, Ru-Xin, Wu, Guo-Xing, Liu, Min-Min, Zhang, Xian-Ming
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.07.2013; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Atoms & subatomic particles; chelates; Chemistry; copper; heterometallic complexes; mixed-valent compounds; self-assembly
• ISSN: 1861-4728; 1861-471X
• DOI: 10.1002/asia.201300143

By using environmentally friendly [Ni(CN)4]2− as a cyanide source, three new heterometallic cyano‐bridged mixed‐valence CuI/CuII coordination polymers with three different electronic configurations (d8–d10), that is, [Cu2Ni(CN)5(H2O)3] (1), [Cu2Ni(CN)5(pn)H2O] (2), and [Cu3Ni(CN)6(pn)2] (3, pn=1,2‐propane diamine) have been synthesized by gradually increasing the amount of pn. Compound 1, which was hydrothermally synthesized in the absence of pn ligand, exhibits the famous 2D Cairo pentagonal tiling, in which the CuI, CuII, and NiII atoms act as trigonal, T‐shaped, and square‐planar nodes, respectively. Notably, there are three water molecules located at the meridianal positions of the octahedrally coordinated CuII atom in compound 1. A similar reaction, except for the addition of a small amount of pn, generated a similar Cairo pentagonal tiling layer in which two of the water molecules that were located at the meridianal positions of the octahedrally coordinated CuII atom were replaced by a chelating pn group. Another similar hydrothermal reaction, with the addition of a larger amount of pn, yielded compound 3, which showed a related two‐fold‐interpenetrated (3,4)‐connected 3D framework with an unprecedented {83}2{86} topology in which the CuII atom was chelated by two pn groups. These structural changes between compounds 1, 2, 3 can be explained by the chelating effect of the pn group. The replacement of two meridianally coordinated water molecules on the octahedral CuII atom in compound 1 by a pn group gives compound 2, which shows similar Cairo tiling, and a further increase in the amount of pn results in the formation of the [Cu(NC)2(pn)2] unit and the two‐fold‐interpenetrated 3D framework of compound 3. The mixed‐valence properties of compounds 1, 2, and 3 were confirmed by variable‐temperature magnetic‐susceptibility measurements. Back of the net: Three heterometallic cyano‐bridged mixed‐valence CuI/CuII coordination networks show Macmahon‐type (5,34) 2D Cairo tiling sheets or a two‐fold‐interpenetrated (3,4)‐connected {83}2{86} 3D topological framework. Their structural difference is due to water molecules on the octahedrally coordinated CuII atom, which are gradually replaced by 1,2‐propane diamine chelate groups.