Bipyridinium Array-Type Porous Polymer Displaying Hydrogen Storage, Charge-Transfer-Type Guest Inclusion, and Tunable Magnetic Properties

A multifunctional pillared-layer porous coordination polymer, {[Mn-2(Bpybc)(ox)(2)]center dot 8H(2)O}(n), has been constructed based on a flexible viologen derivative, 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride (H(2)BpybcCl(2)), and an oxalate (ox) coligand. Single-crystal X-ray analysis reveals that the compound possesses multichannels with dimensions of about 6.1 x 6.6 angstrom along the [110] and [-110] directions and 4.2 x 7.6 angstrom along [100], and a void space of about 41.4%. Hydrogen adsorption measurements at 77 K and 1 atm indicate that the compound exhibits a hydrogen uptake of 0.71 wt%. Owing to the incorporation of bipyridinium acceptor units, the compound can selectively accommodate aromatic donors into its nanosized pores based on charge-transfer interactions in an elastic way, and afford a specific color to different guests. Furthermore, the effect of perturbation exerted by the guest molecules on its magnetic properties has been investigated. The results indicate that the donor inclusion has little effect on its antiferromagnetic behavior, whereas dehydration of the compound decreases the strength of the magnetic exchange couplings and results in a change of the antiferromagnetic transition temperature from 14.7 to 9.8 K.