Oxacalix[4]arenes containing either one or two oxa-bridges afford di and undecanuclear CuII clusters respectively upon reaction with cupric nitrate under facile conditions. Variation in reaction conditions results in formation of a tetranuclear CuII cluster with mono-oxacalix[4]arene, representing a structural expansion of the dinuclear assembly.
![Graphical abstract: Oxacalix[4]arene-supported di-, tetra- and undecanuclear copper(ii) clusters](http://hg.y866.cn/compound/lib/scimg/usr/1/C3DT53088D.jpg)
