Multiplety a) [F(O)PA-O-PB(O)F-O-PA(O)F]2- PA d d d PB d t t
b) [F2(O)PA-O-PB(O)2-O-PA(O)F2]- PA t d PB t qn
c) F2(O)PA-O-PB(O)F-O-PA(O)F2 PA t d d PB d t qn