The diffuse reflectance UV-visible absorption and Raman scattering spectrom
etry provide evidence of sorption of 2,2'-bipyridine (bpy, C10H8N2) as inta
ct molecules into nonacidic MFI zeolites, silicalite-1, and Al-ZSM-5. The e
ffect of the aluminum content n, the nature of the charge-balancing cation
Mn+ as well as bpy loading in M-m/n(AlO2)(m)(SiO2)(96-m) (M(m/n)ZSM-5; m =
0, 3, 6; n =1, 2; M = Na+, Zn2+) were examined. The Raman scattering as wel
l as the X-ray powder diffraction experiments provide evidence of weak stru
ctural deformations of hosts upon bpy sorption. Clear evidence has emerged
from Raman and UV-visible spectroscopic experiments to support the contenti
on that sorption of bpy in dehydrated MFI type zeolites results in three di
fferent bpy conformations according to the aluminum content of the framewor
k and the nature of extraframework cations. The modeling investigations usi
ng Monte Carlo simulations, molecular mechanics, and molecular dynamics cal
culations provide coherent structural support to the interpretation of spec
troscopic results. It appears that the size and shape of straight channel i
tself of MFI type zeolites does not generate energetic and steric constrain
ts to change the trans planar structure of free bpy molecule. Thus, the sor
ption of 2,2'-bipyridine into purely siliceous silicalite-l retains the tra
ns-planar conformation. The nonbonding interactions between the extraframew
ork Na+ cation and occluded bpy in Na(n)ZSM-5 are the main driving forces t
hat stabilize the cisoid nonplanar conformer, whereas the coordination bond
ing between Zn2+ and N atoms in Zn(3)ZSM-5 requires the cis-planar conforma
tion. The spectroscopic and modeling results were found to be in agreement
with previous quantum calculations concerning the conformational behavior o
f free 2,2'-bipyridine relative to the inter-ring rotation.