Liquid crystal behaviour of ionic allylpalladium complexes containing 2-pyrazolylpyridine as bidentate N,N′-ligand

Pyrazole-based allylpalladium complexes: Supramolecular architecture and liquid crystal behaviour

“…The allyl group shows Pd-C distances of ca. 2.10 Å , in agreement with that observed in other Pdcompounds containing N-donor ligands [6,[13][14][15][16][17]. The C9C10C11 allyl group is slightly deviated from the ideal geometry, with bond distances of ca.…”

“…The Pd-N distances of ca. 2.08 Å are similar to those found in related complexes [2,5,6,[13][14][15][16][17]. The allyl group shows Pd-C distances of ca.…”

“…The syntheses of [Pd(g 3 -C 3 H 5 )(Hpz R ) 2 ][BF 4 ] (R = C 6 H 4 OC n H 2n+1 ; n = 12 (I 12 ), 14 (I 14 ), 16 (I 16 ), 18 (I 18 )) [8] were carried out as it has been described for related compounds [6,7]. The spectroscopic (IR and 1 H NMR) and analytical data [9,10] allowed us to establish their identity and they are in agreement with the proposed formulation.…”

“…In this context, we have proved that, in contrast to the mesomorphic nature of 3,5-bis(4-alkyloxyphenyl)pyrazole (Hpz R2 ; R = C 6 H 4 OC n H 2n+1 ) or 2-[3,5-bis(4-alkyloxyphenyl)pyrazol-1-yl]pyridine (pz R2 py) ligands [1][2][3], the 3-substituted homologues Hpz R and pz R py did not exhibit liquid crystal behaviour [4][5][6]. However, it was interesting to note that all of them were able to induce mesomorphism upon co-ordination to determined palladium(II) fragments [2,3,[5][6][7]. In particular, we have observed that the co-ordination of the mesogenic pz R2 py ligands to PdCl 2 or [Pd(g 3 -C 3 H 5 )] + fragments gave rise to metallomesogens [3,7] (Scheme 1).…”

“…In particular, we have observed that the co-ordination of the mesogenic pz R2 py ligands to PdCl 2 or [Pd(g 3 -C 3 H 5 )] + fragments gave rise to metallomesogens [3,7] (Scheme 1). By contrast, the four-coordinated cis-dichloropalladium complexes [PdCl 2 (pz R py)] containing the related 3-substituted pz R py ligands were not mesomoporhic, while their co-ordination to the [Pd(g 3 -C 3 H 5 )] + moiety yielded metallomesogenic derivatives [6] (Scheme1), this feature suggesting the role of the electron delocalisation in the mesomorphism.…”