The conjugate acid of bis{4′-(4-pyridyl)-2,2′:6′,2″-terpyridine}iron(ii) as a self-complementary hydrogen-bonded building block

The protonation of [Fe(1)2]2+, where 1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, generates a trication which forms a one-dimensional, hydrogen-bonded polymer. The single crystal structures of [Fe(1)(H1)][Fe(NCS)6]·2H2O, [Fe(1)(H1)][Fe(NCS)6]·MeCN and [Fe(1)(H1)][ClO4]3·EtOH are reported and illustrate that the packing of the {[Fe(1)(H1)]3+}n chains in the solid state can be modulated by changing the steric demands of the counter-ion. Subtle changes in packing on going from [Fe(1)(H1)][Fe(NCS)6]·2H2O to [Fe(1)(H1)][Fe(NCS)6]·MeCN result in a reorientation of the pendant pyridine rings with respect to the central pyridine ring of the tpy unit in [Fe(1)(H1)]3+.