Pillar chemistry. Part 5. Intercalation of 2,2′-bipyridine, 1,10-phenanthroline, and 2,9-dimethyl-1,10-phenanthroline into γ-zirconium phosphate and formation of interlayer copper(II) complexes

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Abstract
2,2′-Bipyridine (bipy), 1,10-phenanthroline (phen), and 2,9-dimethyl-1,10-phenanthroline (dmphen) can be intercalated into γ-Zr(HPO4)2·2H2O as such (i.e. without first pre-swelling the matrix) to give materials having the final formulation γ-Zr(HPO4)2Lx·n H2O (x= 0.48–0.50). With dmphen, if the γ-Zr(HPO4)2·2H2O is first pre-swelled using ethanol, a further, pure layered phase of composition γ-Zr(HPO4)2(dmphen)0.28·2H2O is obtained; bipy and phen do not give this latter phase. Indirect evidence, X-ray diffraction and i.r. spectroscopy, indicates that the orientations of the amines in the interlayer are different from those in the α-Zr(HPO4)2·H2O analogues, probably due to the presence of specific hydrogen bonding by the interlayer water molecules. All four materials exchange CuII. As expected, given its lower interlayer ligand density compared with the other materials, γ-Zr(HPO4)2(dmphen)0.28·2H2O takes up CuII most readily. Further, within the series γ-Zr(HPO4)2Lx·n H2O the order of uptake, phen > dmphen > bipy, is not that expected from ligand steric requirements alone and the uptake is in all cases slower than that in the α-Zr(HPO4)2·H2O analogues, both results indicating the importance of ligand–matrix interactions. The final pure layered materials obtained have [Cu2 +]: [] ratios of 1:1 [γ-(dmphen)0.28] and 1:2 [γ-dmphen)0.48 and γ-(bipy)0.48]; γ-(phen)0.50 gave [Cu2 +] : []= 0.8:1. Spectroscopic evidence shows that CuII co-ordinates to the amine ligand only in the bipy and phen cases, whereas both dmphen-containing materials exchange Cu2+ into cavities widened by the dmphen but without co-ordination to the intercalated ligand.
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