Hi. Bloemink et al., CHARGE-TRANSFER COMPLEXES OF AMMONIA WITH HALOGENS - NATURE OF THE BINDING IN H3N-CENTER-DOT-CENTER-DOT-CENTER-DOT-BRCL FROM ITS ROTATIONALSPECTRUM, Journal of the Chemical Society. Faraday transactions, 91(5), 1995, pp. 781-787
Citations number
31
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
The ground-state rotational spectra of the four isotopomers (H3N)-N-15
...(BrCl)-Br-79-Cl-35, (H3N)-N-15...(BrCl)-Br-81-Cl-35, (H3N)-N-15...(
BrCl)-Br-79-Cl-37 and (H3N)-N-15...(BrCl)-Br-81-Cl-37 of a complex for
med by ammonia and bromine monochloride have been observed by pulsed-n
ozzle, FT microwave spectroscopy. A fast-mixing nozzle was used to pre
vent a chemical reaction between the components and allow the encounte
r complex to be isolated. The nature of the spectra establishes that t
he observed isotopomers are symmetric-top molecules. Assignment and an
alysis of the spectrum in each case led to the rotational constant B-0
,, the centrifugal distortion constants D-j and D-jk, the halogen nucl
ear quadrupole coupling constants (chi)(Br) and (chi)(Cl), and the com
ponent M(bb)(Br) of the bromine spin-rotation coupling tenser. The rot
ational constants allowed an r(0)-type value of the distance N...Br of
2.627 Angstrom to be established. An r(s)-type method led to the dist
ances r(N Br) = 2.59(1) Angstrom and r(Br-Cl) = 2.186 Angstrom, the fo
rmer requiring a value of B-0 for (H3N)-N-14...(BrCl)-Br-79-Cl-35 obta
ined from unperturbed transition centres estimated without a full hype
rfine structure analysis. A consideration of the intermolecular stretc
hing force constant k(0), determined from D-j, provides evidence of a
relatively strong interaction between the subunits. However, an analys
is of the (chi)(X) (X = Br, Cl) values reveals that the molecular inte
raction is mainly electrostatic in origin, with probably only a small
extent of intermolecular electric charge redistribution on complex for
mation.