problem on locating diradical transition state by DFT

[eric hu <erichu_linux "at@at" yahoo.com>]

Hi, All
 I'm working on a di-phenyl substituted cyclobutane
 diradical intermediate which can either cleavage or
 cyclize to different products. B3LYP/6-31g*
 calculation shows that the singlets are more stable
 than triplets based on the projected species. Now I
 have trouble finding the transition state leading to
 the cyclization pathway. The similar trouble has been
 reported in literature on the similar radical cation
 or diradical system. After coordinate-driving from
 product, I chose some points (with biggest force
 constants) from molden to do the transition state
 opitimization . However, I still can't get the
 resonable transition states. I hope there're other
 ways to deal with this problem. Thanks in advance!
 Eric
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