Synthesis and structural analysis of 2,11-diaza[3.3](3,5)pyridinophaneElectronic supplementary information (ESI) available: 3D coordinates for compounds 1 and 6 and for the three calculated conformers of compound 1 (1BB, 1CB and 1CC). See http://www.rsc.org/suppdata/p2/b2/b200402j/