Mixed crystals intermolecular interactions

G. G. Ferenezy and J. G. Angyan Intra- and intermolecular interactions in crystals of polar molecules. A study by the mixed quantum mechanics/molecular mechanical SCMP-NDDO method, J. Comp. Chem. 22, 1679-1690 (2001). 

As described below, investigations on the design and synthesis of photore-active mixed molecular crystals are still very limited in number and scope. However, by very ingenious manipulation of the above-mentioned intermolecular interactions, construction of new crystals bearing desired reactivities should be possible for many types of bimolecular photoreaction. Mote investigations in this direction should be carried out. 

Equations (5.18) and (5.20) are special cases of the more general formulas derived in Ch. 3 they demonstrate for the given crystal model how the mixing of molecular configurations due to intermolecular interaction in the crystal affects the oscillator strengths of the dipole transitions. We shall only stress here the... 

Most organic compounds contain heteroatoms and the intermolecular interactions in their crystal are a complex mosaic of forces of varying strengths, directionalities and distance dependence characteristics [2,5,6]. In such situations, direct and simple extrapolations from molecular to crystal structiue are tricky and difficult in the best cases and impossible in the worst We present here two examples of molecule crystal extrapolation to convey the mixed feelings... 

For the removal of intermolecular interactions between analyte molecules a large excess of matrix molecules is required. Insoluble or poorly soluble polymers do not readily form mixed poly-mer/matrix crystals, a requirement for preparing... 

Awaga, K., Sugano, T., and Kinoshita, M., Ferromagnetic intermolecular interactions in a series of organic mixed-crystals of galvinoxyl radical and its precursory closed shell compound, J. Chem. Phys., 85, 2211, 1986. 

Afterwards, the susceptibility of the 1 1 mixed crystal of TNN and closed shell 1,3,5-trinitrobenzene was measured [20]. In this case, TNN molecules are considered to be nearly isolated from one another and the magnetism of the triradical itself can be observed except at very low temperatures. The susceptibility at 250 K seems to be a reasonable value corresponding to an assembly of three independent 5=1/2 species. When the temperature is lowered, the intramolecular FM coupling of JJk = - - 23 K is observed as an increase of XpT in the middle temperature region, and then the intermolecular AFM interactions become effective at the lower temperature. 

As for interactions between hke molecules, our infonnation comes mainly from the thermodynamic properties of gases at low densities and from the transport properties in dilute gases. No experimental study of intermolecular forces on the basis of thermodynamic properties of mixed crystals near 0 K has been performed imtil now. 

---