Understanding why crystallization in strong magnetic fields can lead to new polymorphs requires methods to calculate the diamagnetic response of organic molecular crystals. We develop the calculation of the macroscopic diamagnetic susceptibility tensor, χ cryst , for organic molecular crystals using periodic density functional methods. The crystal magnetic susceptibility tensor, χ cryst , for all experimentally known polymorphs, and its molecular counterpart, χ mol , are calculated for flexible pharmaceuticals such as carbamazepine, flufenamic acid, and chalcones, and rigid molecules, such as benzene, pyridine, acridine, anthracene, and coronene, whose molecular magnetic properties have been traditionally studied. A tensor addition method is developed to approximate the crystal diamagnetic susceptibility tensor, χ cryst , from the molecular one, χ mol , giving good agreement with those calculated directly using the more costly periodic density functional method for χ cryst . The response of pharmaceutical molecules and crystals to magnetic fields, as embodied by χ cryst , is largely determined by the packing in the crystal, as well as the molecular conformation. The anisotropy of χ cryst can vary considerably between polymorphs though the isotropic terms are fairly constant. The implications for developing a computational method for predicting whether crystallization in a magnetic field could produce a novel or different polymorph are discussed.

In this research, the absorbance and luminescence response of two osmium(II) phenathrane (phen) carbonyl complexes to various DNA, heparin and i-carrageenan polyanions were studied. The [Os(phen) 2 CO(L)] 2+ complexes with L either a 4-phenyl pyridine (4-phpy) or phenyl imidazole (phimd) group exhibit moderate luminescent intensity in the visible region, their intensities are highly altered by the addition of DNA and other polyanion samples. These luminescent responses to polyanions were also compared with the [Ru(phen) 3 ] 2+ complex. In ethanol solution, the presence of polyanions significantly enhanced the luminescent emission intensity of [Os(phen) 2 CO(L)] 2+ complexes with a blue shift. While the polyanions all showed emission enhancement on the highly luminescent [Ru(phen) 3 ] 2+ complex in ethanol solution with a red spectra shift. The [Os(phen) 2 CO(L)] 2+ with (phimd) ligand has the lowest emission in ethanol solution, its intensity can be enhanced up to 11 times in the presence of DNA polyanions. This enhancement for all the complexes in ethanol is mainly due to their electrostatic interaction with the anion sites and with some degree of ligand intercalation into the polyanion hydrophobic structure which reduced the solvent quenching of the complexes. The blue shift of the (4-phpy) and particularly (phimd) Os(II)CO complexes indicate an insertion of the (4-phpy) or (phimd) group into the polymer chains. The two new Os(II)CO complexes has great potential to be used as luminescence sensors for DNA and polyanion detection in the low micro molar range with high sensitivity.