New highly phenylated bis(phthalic) and bis(naphthalic) anhydrides and polyimides therefrom - Polyimides and Other High Temperature Polymers - page 101

The reaction of 4,4'-bis(2,4,5-triphenylcyclopentadien-l-on-3-yl)benzophenone

( ) [22] with a twofold molar amount of maleic anhydride in boiling bromoben-

zene, followed by dehydrogenation with bromine, yielded dianhydride

I

. This
white crystalline compound showed good solubility in conventional organic sol-
vents - N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), tetrahydro-
furan (THF), chloroform, toluene, etc.
The structure of compound

II

was confirmed by elemental analysis, 1 H and 13 C
NMR, and FTIR spectroscopies. The above reaction was monitored by IR spec-
troscopy, in particular, by the disappearance of the intense band at 1709 cm -1 cor-
responding to the carbonyl of the cyclopentadienone moiety.
The IR spectrum of compound

II

shows absorption bands at 1843 and 1779 cm -1 ,
which are characteristic of the stretching vibrations of the carbonyl of phthalic an-
hydride, along with an intense absorption band at 1663 cm -1 , which corresponds to
the stretching vibrations of the carbonyl of the benzophenone moiety.
The 1 H NMR spectrum of compound

II

= 6.85 ppm (d,
4H, J = 8.1 Hz) and four multiplets corresponding to the other aromatic protons,
while the 13 C NMR spectrum shows signals in the region of

II exhibits a signal at δ

= 195.28 ppm,
characteristic of the carbonyl of the benzophenone moiety, and an intense signal
at

δ

= 161.21 ppm corresponding to the four almost equivalent carbons of the di-
anhydride

δ

carbonyl groups.
NMR spectra do not provide information about the spatial arrangement of phenyl
rings. Moreover, X-ray diffraction data were unavailable for compound

II

There-
fore, we carried out a series of calculations to gain insight in their special arrange-
ment. In this work we made no attempt to calculate all possible conformations of
compound

II .

. The geometry of one of these conformations was estimated by the
quantum semiempirical method PM3. The calculations showed that the benzene
rings attached to the phthalic anhydride moiety were not in the same plane as the
aromatic ring of the anhydride. The corresponding torsional angles that characterize
the rotation angles of benzene rings relative to the phthalic anhydride together with
the most typical bond lengths are summarized in Table 1. (Note the calculations
showed that the distances between the H at C(19) and the H at C(90) (1.718 Å), and
between the H at C(18) and the H at C(67) (2.645 Å) were very small lending sup-
port to the statement that compound

II

was completely noncoplanar.) This is an ad-
ditional explanation for the high solubility of compound

II

II .

with a twofold molar amount of 4-(phenyl-
ethynyl)naphthalic anhydride [23] by the Diels-Alder reaction in boiling 1,2,4-
trichlorobenzene produced the new bis(naphthalic anhydride) - 4,4'-bis[2,3,5,6-
tetraphenyl(4,5-dicarboxynaphth-1-yl)phenyl]benzophenone dianhydride (

The reaction of compound I

)
with a yield of 91%. The product was isolated as a pale-yellow amorphous sub-
stance showing good solubility in conventional organic solvents. The reaction was
monitored by Raman spectroscopy by measuring the intensity of the band at 1709
cm -1 corresponding to the carbonyl of the cyclopentadienone moiety.

III