Blue- and green-emitting cyclometalated liquid-crystalline iridium complexes are realized by using a modular strategy based on strongly mesogenic groups attached to an acetylacetonate ancillary ligand. The cyclometalated ligand dictates the photophysical properties of the materials, which are identical to those of the parent complexes. High hole mobilities, up to 0.004 cm² V⁻¹ s⁻¹, were achieved after thermal annealing, while amorphous materials show hole mobilities of only approximately 10⁻⁷–10⁻⁶ cm² V⁻¹ s⁻¹, similar to simple iridium complexes. The design strategy allows the facile preparation of phosphorescent liquid-crystalline complexes with fine-tuned photophysical properties.

The luminescent and mesomorphic properties of a series of metal complexes based on hexacatenar 2,2′:6′,2′′-terpyridines are investigated using experimental methods and density functional theory (DFT). Two types of ligand are examined, namely 5,5′′-di(3,4,5-trialkoxyphenyl)terpyridine with or without a fused cyclopentene ring on each pyridine and their complexes were prepared with the following transition metals: Zn^II, Co^III, Rh^III, Ir^III, Eu^III and Dy^III. The exact geometry of some of these complexes was determined by single X-ray diffraction. All complexes with long alkyl chains were found to be liquid crystalline, which property was induced on complexation. The liquid-crystalline behaviour of the complexes was studied by polarising optical microscopy and small-angle X-ray diffraction. Some of the transition metal complexes (for example, those with Zn^II and Ir^III) are luminescent in solution, the solid state and the mesophase; their photophysical properties were studied both experimentally and using DFT methods (M06-2X and B3LYP).

Co-crystallisation of, in particular, 4-iodotetrafluorophenol with a series of secondary and tertiary cyclic amines results in deprotonation of the phenol and formation of the corresponding ammonium phenate. Careful examination of the X-ray single-crystal structures shows that the phenate anion develops a CO double bond and that the CC bond lengths in the ring suggest a Meissenheimer-like delocalisation. This delocalisation is supported by the geometry of the phenate anion optimised at the MP2(Full) level of theory within the aug-cc-pVDZ basis (aug-cc-pVDZ-PP on I) and by natural bond orbital (NBO) analyses. With sp² hybridisation at the phenate oxygen atom, there is strong preference for the formation of two non-covalent interactions with the oxygen sp² lone pairs and, in the case of secondary amines, this occurs through hydrogen bonding to the ammonium hydrogen atoms. However, where tertiary amines are concerned, there are insufficient hydrogen atoms available and so an electrophilic iodine atom from a neighbouring 4-iodotetrafluorophenate group forms an I⋅⋅⋅O halogen bond to give the second interaction. However, in some co-crystals with secondary amines, it is also found that in addition to the two hydrogen bonds forming with the phenate oxygen sp² lone pairs, there is an additional intermolecular I⋅⋅⋅O halogen bond in which the electrophilic iodine atom interacts with the CO π-system. All attempts to reproduce this behaviour with 4-bromotetrafluorophenol were unsuccessful. These structural motifs are significant as they reproduce extremely well, in low-molar-mass synthetic systems, motifs found by Ho and co-workers when examining halogen-bonding interactions in biological systems. The analogy is cemented through the structures of co-crystals of 1,4-diiodotetrafluorobenzene with acetamide and with N-methylbenzamide, which, as designed models, demonstrate the orthogonality of hydrogen and halogen bonding proposed in Ho’s biological study.

The dimeric di-μ-chlorido anion hexachloridopalladate(II)platinate(II) has been prepared as a mixture with hexachloridodipalladate(II) and hexachloridodiplatinate(II) and has been identified by using a combination of X-ray crystallography and ¹⁹⁵Pt NMR spectroscopy. This is the first report of a heterodinuclear dimer of this type.

48 new hydrogen-bonded complexes have been prepared by combining 16 fluorophenols of general formula C₆F_nH_5−nOH with three different alkoxystilbazoles (butyloxy-, octyloxy- and dodecyloxy-). Single-crystal X-ray structures were obtained for 10 of the 16 complexes of octyloxystilbazole from which it was found that most of the structures could be collected into one of two groups according to both the motif shown by the complex and by the solid-state packing. Because all but one crystallised in the P space group, meaningful comparisons could be drawn and it was observed that six structures were extremely close in nature so that significant molecular overlap was found. On this basis, doubt is cast on the significance of some of the weaker intermolecular contacts found in the solid state. 40 of the new complexes showed liquid-crystal properties and it was found that although complexes of butyloxystilbazole were all nematic, almost all of those with dodecyloxystilbazole showed a smectic A (SmA) phase. Complexes of octyloxystilbazole showed a mixture of both. Structure/property correlations showed that clearing points were independent of the pK_a of the phenol. The most stable mesophases were found when the fluorophenol contained a fluorine at the 2-position, which was interpreted in terms of the formation of an intramolecular H⋅⋅⋅F hydrogen bond to give a six-membered ring linking the two components into a stable, coplanar conformation. The least stable mesophases were found when no such ring formation was possible and the phenol was relatively free to move.