E Vessally - Payame Noor University, Department of Science, P. O. Box: ۱۹ ۳۹۵-۴۶۹۷ Tehran, Iran
H Ghoudarzi Afshar - Depart ment of Chemistry, University of Ilam, Ilam
M Niko orazm - Depart ment of Chemistry, University of Ilam, Ilam
Eynollah abolfathi - Depart ment of Chemistry, University of Ilam, Ilam

Dival ent carbenes and their analogues are strongly r eactive and their derivatives have played important roles as transient intermediate a nd powerful reagents [۱ -۲]. the sin glet-triplet energy splitti ng could be related to several effects. The singlet sta te should be stabilize d by substituents that are electro negative and/or have electron pairsthat can be donated via hyper conjugation to the em pty ı orbita l. The tripl et state, on the other hand, should be stabilized by substituents that are bulky and/or electropositive. The sterically demanding groups may be e mployed as a stabilizer for a variety of highly reactive heavy carbenes [۳]. Follo w up on our work [۴], t he density f unctional theory ( DFT) calculation were carrie d out to stu dy the Steric effects at Į-position on the singlet -triplet splitting R۲C۶H۶M (R= –H, -CH۳, i-Pr , t-Bu , and M = C, Si , Ge). Other geometrical parameters such as bo nd lengths, bond angles , Mulliken charge at ato ms, dipole Moment (D ) and dihedral angles we re calculated and discussed.

Steric effects, energy gaps, Į-Position, D FT method