Department of Physics, Sri Venkateswara University,Tirupati^* Department of Physics,Sri Venkateswara University,Tirupati - 517 502^** Department of Chemistry,Sri Venkateswara University,Tirupati - 517 502^*** Center For Materials Characterisation,National Chemical Laboratory, Pune^****
○Musali Krishnaiah^* Jadaprolu Radhakrishna^** Reddy Suresh C^*** Puranik Vedavati G^****

Organophosphorus heterocycles with phosphoryl unit exhibit significant physiological activity depending on their size, electrophilic character of phosphorus, the strength of the bond p-x and steric nature of the substitutents. These compounds find applications as pesticides, nerve gases, antioxidants and as stabilizers in polymer and oil industries. The structures P2₁/c & P2₁/n of the title compounds are determined to know the effect of substituents on the conformation of dioxaphosphepine ring.

The dioxaphosphepine rings exhibit twist - chair form for the former where as a distorted boat conformation for the later. Fusion of the phosphepine ring to the biphenyl system causes strain, as evidenced by both widening and compression of the endocyclic angles in the heterocyclic ring.