MoleculargValues, Magnetic Susceptibilities, Molecular Quadrupole Moments, and Sign of the Electric Dipole Moment in Cyclopropene

摘要

The highhyphen;field rotational Zeeman effect has been studied in cyclopropene and 1,2hyphen;dideuterocyclopropene. The moleculargvalues for cyclopropene aregaathinsp;equals;thinsp;minus;0.0897thinsp;plusmn;thinsp;0.0009, gbbthinsp;equals;thinsp;minus;0.14915thinsp;plusmn;thinsp;0.00016, andgccthinsp;equals;thinsp;0.05363thinsp;plusmn;thinsp;0.00077. For the deuterated species they aregaathinsp;equals;thinsp;minus;0.0689thinsp;plusmn;thinsp;0.0010, gbbthinsp;equals;thinsp;minus;0.13718thinsp;plusmn;thinsp;0.00015, andgccthinsp;equals;thinsp;0.4538thinsp;plusmn;thinsp;0.00018. The magnetic susceptibility anisotropies, in units of 10minus;6erg/G2middot;mole, are2khgr;aathinsp;minus;thinsp;khgr;bbthinsp;minus;thinsp;khgr;ccthinsp;equals;thinsp;7.1thinsp;plusmn;thinsp;0.6andminus;khgr;aathinsp;plus;thinsp;2khgr;bbthinsp;minus;thinsp;khgr;ccthinsp;equals;thinsp;26.8thinsp;plusmn;thinsp;0.4. Although only the relative signs of thegvalues are determined experimentally, the above signs are conclusively assigned on the basis of the molecular quadrupole moments. Theaaxis is perpendicular to the double bond, and theaandbaxes are in the molecular plane. The molecular quadrupole moments in cyclopropene, in units of 10minus;26esumiddot;cm2, areQaathinsp;equals;thinsp;minus;0.4thinsp;plusmn;thinsp;0.4, Qbbthinsp;equals;thinsp;2.4thinsp;plusmn;thinsp;0.3, andQccthinsp;equals;thinsp;minus;2.0thinsp;plusmn;thinsp;0.6. Using the known molecular structure, the diagonal elements of the paramagnetic susceptibility tensor and the anisotropies in the second moment of the electronic charge distribution may be calculated, and they arekhgr;aapthinsp;equals;thinsp;56.1thinsp;plusmn;thinsp;0.3, khgr;bbpthinsp;equals;thinsp;80.7thinsp;plusmn;thinsp;0.2, khgr;ccpthinsp;equals;thinsp;93.4thinsp;plusmn;thinsp;0.2, all in units of 10minus;6erg/G2middot;mole; andlang;a2rang;thinsp;minus;thinsp;lang;b2rang;thinsp;equals;thinsp;4.26thinsp;plusmn;thinsp;0.2, lang;b2rang;thinsp;minus;thinsp;lang;c2rang;thinsp;equals;thinsp;7.75thinsp;plusmn;thinsp;0.2, andlang;c2rang;thinsp;minus;thinsp;lang;a2rang;thinsp;equals;thinsp;minus;12.01thinsp;plusmn;thinsp;0.2, all in units of 10minus;16cm2. Although the bulk susceptibility is unknown, a theoretical value oflang;c2rang;in conjunction with the measured secondhyphen;moment anisotropies enables the diagonal elements of the diamagnetic and total magnetic susceptibility tensors to be predicted. These arekhgr;aadthinsp;equals;thinsp;minus;82.3thinsp;plusmn;thinsp;0.3, khgr;bbdthinsp;equals;thinsp;minus;100.4thinsp;plusmn;thinsp;0.3, khgr;ccdthinsp;equals;thinsp;minus;133.3thinsp;plusmn;thinsp;0.3, khgr;aathinsp;equals;thinsp;minus;26.2thinsp;plusmn;thinsp;0.4, khgr;bbthinsp;equals;thinsp;minus;19.7thinsp;plusmn;thinsp;0.4, khgr;ccthinsp;equals;thinsp;minus;39.9thinsp;plusmn;thinsp;0.4, andkhgr;Avthinsp;equals;thinsp;minus;28.6thinsp;plusmn;thinsp;0.5, all in units of 10minus;6erg/G2mole. The sign of the electric dipole moment is obtained from accurately measuredgvalues in the two isotopic species, and gives a polarity of plus;vltri;minus;.