Heteromolecular

Examples of crystalline associates where dimethyl sulfoxide is involved as one of the heteromolecular constituents are known in an appreciable number1. Certainly the associate between dimethyl sulfoxide and trimesic acid 84 (cf. Chapter 5 in Vol. 140 of this series) is one of the important individual cases. Characteristic modes of association between the carboxylic hosts discussed here and dimethyl sulfoxide are illustrated in Fig. 24. Pertinent geometry data are listed in Tables 17 and 18. One may realize from Fig. 24 that the fundamental mode of association of the host acids 20, 26, 37, and 41 is the formation of discrete H-bonded islands of host and (usually) one guest molecule. 

Kochi and co-workers engineered heteromolecular charge-transfer crystals of a tricyclic dithiin 34 stacked alternately with anthracene, which can undergo spontaneous Diels-Alder cycloaddition to give a novel artificial crystal system <2001JA87, 2001JA4951>. 

Seeds of isostructural or quasi-isostructural species that crystalUze well can also been employed to induce crystalUzation of unyielding materials [61]. Heteromolecular seeding [62], whereby near isostructural compounds can be used to template crystallization in less accessible or elusive desired crystal forms, can be apphed. For instance, chiral co-crystals of tryptamine and hy-drocinnamic acid were prepared by crystalUzation in the presence of seeds of different chiral crystals [63]. Of course, imintentional seeding may also alter the crystalUzation process in an undesired manner [64]. 

Roedel, W., Measurement of Sulfuric Acid Saturation Vapor Pressure Implications for Aerosol Formation by Heteromolecular Nucleation, J. Aerosol Sci., 10, 375-386 (1979). 

It is emphasized that the terms excimer2 and exciplex3,4 are reserved here for homomolecular and heteromolecular excited double molecules formed after the act of light absorption by one component in a process of photoassociation, in the absence of spectroscopic or cryoscopic evidence for molecular association in the ground state. Recent findings indicate that excimer (or exciplex) formation may also result from triplet-triplet annihilation,5,8 cation-anion combination7 (doublet-doublet-annihilation), and electron capture by the (relatively stable) dimer (or complex) cation8 these processes are discussed in Section VII. 

Enthalpies and Entropies of Heteromolecular Photoassociation of Donor (D) and Acceptor (A) in Hexane Solution30... 

Heteromolecular -complexes of aromatic cation radicals have been designed from the complexation of aromatic cation radical with a different neutral aromatic donor but such ionic K-heterocomplexes were observed as metastable species in the gas phase or in freon matrices57 58. 

If both A and B are polyatomic relaxing gases, there will also be two collision processes, corresponding to (1) and (2), for vibration-translation energy transfer from B in homomolecular and heteromolecular collisions. In addition there can be a vibration-vibration transfer between A and B, making five transfer processes in all... 

Comparison of the collision numbers given above for vibration-vibration transfer with those for vibration-translation, given in Section 4, shows that in many cases vibration-vibration transfer between two resonant or near-resonant modes is much more efficient than vibration-translation transfer from either. This applies equally to homomolecular and heteromolecular collisions, and carries the interesting consequence that the quickest route for vibrational excitation of upper levels from the ground level by homomolecular collisions is an initial vibration-translation excitation to the v = 1 level, followed by successive vibration-vibration transfers to higher levels. Because of the selection rule, Av = 1,... 

Heteromolecular seeding, in crystal engineering, 12, 581 Heteronuclear alkynylcopper complexes, characteristics,... 

T. Frii, A.V. Trask, W.D.S. Motherwell, W. Jones, Guest-directed assembly of caffeine and succinic acid into topologically different heteromolecular host networks upon grinding, Cryst. Growth Des. 8 (2008) 1605-1609. 

R. Basu, N. P. Guisinger, M. E. Greene and M. C. Hersam, Room temperature nanofabrication of atomically registered heteromolecular organosilicon nanostructures using multistep feedback controlled lithography, Appl. Phys. Lett. 85, 2619 (2004). 

The heteromolecular production of particles in a vapor mixture is estimated from a model similar to the homogeneous case above. However, the production rate depends on the energy of formation of mixed embryos, the composition of which depends on the thermodynamic properties of the mixture. 

Fig. 7.1 General scheme representing peroxidase-mediated reactions (a) homopolymerization, (b) heteromolecular coupling, (c) cross-linking, and (d) surface functionalization...

Nucleation processes, especially in nature, are rarely homomolecular and homogeneous usually two species are involved (binary heteromolecular nucleation), and foreign surfaces may also be present (heterogeneous... 

Figure 14 Precipitation of [(r 5-C5H5)2Fe]+ as its [AsFg]- salt generates two concomitant crystals a trigonal phase (Fe-T) and a monoclinic phase (Fe-M), which can be separated out by heteromolecular seeding with isomorphous crystals of trigonal [(r 5-C5Fl5)2Co][AsF6] and of monoclinic [(r 5C5Fl5)2Fe][PF6]. The crystals are sufficiently robust to undergo a full cycle of four phase transitions directly on the diffractometer, Fe-T — Fe-M — Fe-C — Fe-M - Fe-T.

When two or more molecules of the same type associate, so-called homo-intermolecular hydrogen bonds are formed (Fig. 2-4). The association of different molecules e.g. R—O—H- -NRj) results in hetero-intermolecular hydrogen bonds. The designations homo- and heteromolecular [192] as well as homo- and heteroconjugated hydrogen bond are also in use. A remarkable example of a competitive solvent-dependent equilibrium between homo- and hetero-intermolecular hydrogen-bond associated species has been found in solutions of 4-hydroxyacetophenone and 2-(2-hexyloxyethoxy)ethanol [319]. 

Elements of Group IV clusters. Investigation of C0-02 mixtures also revealed reactions between Ol and CO. The role of impurity reactions involving H20 is considered in detail and the implications of all data to the vapour-phase radiolysis of C02 are discussed.202 A wide range of heteromolecular clusters containing CO and/or C02 together with S02, NO, or H20 has been found in isentropically expanding jets 203 the observed clusters and their formation conditions are summarized in Table 12. These clusters, particularly the hydrates, are of importance in atmospheric chemistry since favourable conditions for their formation are known to be present in jet-aircraft exhausts.203... 

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