Heteronuclear intramolecular

HETERONUCLEAR INTRAMOLECULAR RESONANCE-ASSISTED HYDROGEN BONDS... 

It is worth mentioning that there are numerous studies of intramolecular RAHBs. For example, one can refer to the sound studies of Buemi and Zuccarello [13, 31]. There are investigations of homonuclear and heteronuclear intramolecular RAHBs [13, 31, 32], and not only were O-H- - -O, N-H- - -O, and O-H- -N studied, but also other more exotic systems such as O-H- - -S... 

The most common strategy in the synthesis of heteronuclear complexes is the use of bidentate donor ligands bearing different donor centers. In that way both donor atoms can be coordinated selectively to two different metal centers in a consecutive way. If the space between the donor atoms of the ligands is short, interactions between both metals usually appear, normally intramolecular. Sometimes, albeit not very often, the bidentate units bind to one another, leading to extended structures through metallophilic interactions. As we have commented, in the case of gold-silver derivatives the number of luminescent studies of these derivatives is very scarce. 

Combination modes of intramolecular vibrations cannot occur in diatomic molecules. The near infrared spectra of heteronuclear diatomics only consist of overtone components and, if measured at an appropriate optical path length, these spectra appear like... 

Prompers and Briischweiler showed by quasiharmonic analysis that the conformational partition function of a globular protein sampled on the ns time scale can be factorized in good approximation into purely reorientational part, which determines heteronuclear NMR spin relaxation, and a remaining part that includes other types of intramolecular motions. Thus a thermodynamic interpretation of NMR relaxation parameters in proteins in the presence of motional correlations can be given. 

As stated in the previous section, dynamic behaviour involving intramolecular rearrangements of the metal skeletons of Group 11 metal heteronuclear clusters is relatively common, in marked contrast to the situation observed for almost all other transition metal clusters, which have metal frameworks that are stereochemically rigid in solution. The mechanisms of these metal core rearrangements are, therefore, of considerable interest. 

Palmer AG, Ranee M, Wright PE (1991) Intramolecular motions of a zinc finger DNA-binding domain from Xfin characterized by proton-detected natural abundance 13 C heteronuclear NMR spectroscopy. J Am Chem Soc 113 4371-4380... 

Temperature Dependence of Spin-Lattice Relaxation. The spin-lattice relaxation rate T ) is comprised of various contributions to the relaxation process, including homo- and heteronuclear dipolar interactions, quadrupolar interactions, chemical shift anisotropy, spin-rotation, and others (10). When the relaxation mechanism is dominated by inter- and intramolecular dipole-dipole interactions, the will increase with temperature, pass through a maximum, and decrease with increasing temperature. Since the relaxation rate is the inverse of the relaxation time, the Ti will decrease, pass through a minimum (Timin), and then increase with increasing temperature (77). The T lmin values are proportional to the internuclear distances. 

The 2D spectra in solid state direcdy probe intermolecular or intramolecular interactions through correlations between specific sites, mainly produced by homonuclear and heteronuclear dipolar coupfings. Then through these 2D spectra, it is possible to provide a better assignment in complex spectra, obtain high-resolution spectra and retrieve direct information on distance, proximity, bonding, n-n interactions, ring currents, etc. 

A mdimentary H-bond nomenclature is given in Scheme 5. H-bonds can be classified according to their strength as weak, moderate, or strong proton position as symmetric (or centric, or proton-centred) or asymmetric X-H-Y angular value as bent or linear (5.1a,b) chemical symmetry as homonuclear or heteronuclear (5.IIa,b) connectivity as two-centered, three-centered (or bifurcated), or chelated (5.IIIa-c) and topology as intermolecular (5.IVa-c) or intramolecular (5.IVd). As a mle, homonuclear H-bonds tend to be stronger than heteronuclear, two-centered than multicentered, and linear than bent ones. 

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