Sometimes the same, sometimes different: understanding self-assembly algorithms in coordination networks

The syntheses and characterizations of three new ligands containing two 4,2':6',4"-tpy or two 3,2':6',3"-tpy metal-binding domains are reported. The ligands possess different alkyloxy functionalities attached to the central phenylene spacer: n -pentyloxy in 3 , 4-phenyl- n -butoxy in 4 , benzyloxy in 5 . Crystal growth under ambient conditions has led to the formation of {[Co(NCS) 2 ( 3 )]·0.8C 6 H 4 Cl 2 } n and {[Co(NCS) 2 ( 4 )]·1.6H 2 O·1.2C 6 H 4 Cl 2 } n , with structures confirmed by single crystal X-ray diffraction. Both the cobalt(II) centre and ligand 3 or 4 act as 4-connecting nodes and both {[Co(NCS) 2 ( 3 )]·0.8C 6 H 4 Cl 2 } n and {[Co(NCS) 2 ( 4 )]·1.6H 2 O·1.2C 6 H 4 Cl 2 } n possess a 3D cds net despite the fact that 3 and 4 contain two 4,2':6',4"-tpy and two 3,2':6',3"-tpy units, respectively. Taken in conjunction with previously reported data, the results indicate that the role of the alkyloxy substituent is more significant than the choice of 4,2':6',4"- or 3,2':6',3"-tpy isomer in determining the assembly of a particular 3D net. The combination of Co(NCS) 2 with 5 resulted in the formation of the discrete molecular complex [Co(NCS) 2 (MeOH) 2 ( 5 ) 2 ]·2CHCl 3 ·2MeOH in which 5 acts as a monodentate ligand. The pendant phenyls and both coordinated and non-coordinated 4,2':6',4"-tpy units are involved in efficient π-stacking interactions