Synthesis, Structural Isomerism, and Magnetism of Extended Framework Compounds of Type [Cu (dca)2(pyz)]n, Where dca=Dicyanamide (N(CN)−2) and pyz=Pyrazine

✍ Scribed by Paul Jensen; Stuart R. Batten; Gary D. Fallon; David C.R. Hockless; Boujemaa Moubaraki; Keith S. Murray; Richard Robson

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 282 KB
• Volume: 145
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1998.8082

✦ Synopsis

Two structural isomers of the dicyanamide (dca, N(CN) ؊

2 ) complex [Cu(dca) 2 (pyz)] n (pyz ‫؍‬ pyrazine) were prepared from aqueous solution and crystals were grown by slow di4usion and gel techniques. Crystal data: -[Cu(dca) 2 (pyz)] n , CuC 8 H 4 N 8 , monoclinic, Pn, Z ‫؍‬ 16, a ‫؍‬ 24.2549(7) A > , b ‫؍‬ 6.8571(2) A > , c ‫؍‬ 24.6445(7) A > , ‫؍‬ 91.023(2)3, V ‫؍‬ 4098.2(2) A > 3 , R(F) ‫؍‬ 0.0466 (F' '4 (F)), R w (F 2 ) ‫؍‬ 0.0939 (all data); -[Cu(dca) 2 (pyz)] n , CuC 8 H 4 N 8 , monoclinic, C2/m, Z ‫؍‬ 2, a ‫؍‬ 9.7659(8) A > , b ‫؍‬ 6.8787(7) A > , c ‫؍‬ 7.3870(5) A > , ‫؍‬ 95.254(7)3, V ‫؍‬ 494.15(6) A > 3 , R(F) ‫؍‬ 0.038, R w (F) ‫؍‬ 0.074 (I' '3 (I)). The -isomer consists of two interpenetrating -Po related networks, while theisomer contains sheets composed of Cu(dca) 2 chains linked by bridging pyz ligands.

Despite the di4erences in their network structures, the magnetic properties of these structural isomers are essentially the same. Weak antiferromagnetic coupling of the S ‫؍‬ 1/2 centers leads to a maximum in susceptibility at 3.5 K. One of the aims of this work is to prepare long-range ordered materials but no magnetic order is observed in the present compounds. The antiferromagnetic coupling is a little stronger than that in the parent Cu(dca) 2 but of similar strength to that in chain compounds of type [Cu(dca) 2 (imidazole) 2 ] n . Thus, the pyz linkers enhance the coupling to only a small degree. The networks in the -isomer behave independently and identically from the magnetic point of view.