The high-field rotational Zeeman effect has been observed in formyl fluoride (CHFO), vinyl fluoride (CH2CHF), trifluoroethylene (CF2CHF), ethyl fluoride (CH3CH2F), and 1, 1-difluoroethane (CH3CHF2). The signs and magnitudes of the magnetic susceptibility anisotropies [(2χaa − χbb − χcc) and (2χbb − χaa − χcc)] and the magnitudes of the molecular g values (gaa, gbb, and gcc) were obtained and are listed. Although only the relative signs of the g values could be obtained by experiment, the signs were determined through analysis of molecular quadrupole moments and the second moments of the electronic charge distribution. The molecular quadrupole moments (Qaa, Qbb, and Qcc) are also given. Using the magnetic susceptibility anisotropies, g values, the known structures, and the bulk susceptibilities, the diagonal elements of the paramagnetic, diamagnetic, and total susceptibility tensors were calculated along with the second moments of the electronic charge distribution.
The linear and quadratic rotational Zeeman effect in HOF has been observed with a high magnetic field. The magnetic susceptibility anisotropies are 2χaa −χbb −χcc = (−19.6±0.6) × 10−6 erg/G2·mole and 2χbb −χaa −χcc = 12.8±1.2 (the a axis is nearly along the OF bond and the c axis is perpendicular to the molecular plane); the molecular g values are gaa = 0.642±0.001, gbb = −0.119±0.001, and gcc = −0.061±0.001 and the molecular quadrupole moments are Qaa = (0.2±0.4)×10−26 esu · cm2, Qbb = 1.9±0.8, and Qcc = −2.1±1.1. These results are compared with H2O and F2O. The effect of in-plane fluorine substitution on the out-of-plane minus the average in-plane magnetic susceptibility anisotropy, Δχ, is discussed for a number of molecules and additive values are obtained for each successive fluorine substitution for planar molecules. These contributions to Δχ are first fluorine = +4.5±1.2, second F = +2.5±1.1, and third F = +0.6±0.8. These trends are explained in terms of changes in hybridization of the atom to which the fluorine is bonded. These values are used with results on mono- and difluorobenzene to estimate Δχ for benzene and trifluorobenzene. The electric dipole moments were obtained by the Stark effect and are HOF: μa = |0.37|±0.10 and μb = |2.20|±0.10. The total electric dipole moment of HOF is μ = |2.23|±0.10 D. The electronic structure of HOF is discussed in light of these results.
The high-field rotational Zeeman effect has been observed in thioformaldehyde. The magnetic susceptibility anisotropies are 2Xaa-Xbb-Xcc=S2.3± 1.1 (X 10-j! erg/G2· mole) and 2Xbb-Xaa-Xcc= -S.1± 0.7. The molecular g values with uniquely determined signs are gaa= -S.2602±0.OO68, gbb= -0.1337± 0.0004, and gcc= -0.0239±0.0004. c is the out-of-plane axis and the a axis is the dipole axis. gaa represents the largest molecular g value yet measured. Use of these five Zeeman parameters and the known structure gives the molecular quadrupole moments: Qaa=3.0±0.7(Xto-26 esu·cm 2 ), Qbb=-2.4±0.S, Qcc=-0.6± 1.1; the diagonal elements of the paramagnetic susceptibility tensor: Xaa P = 4S.8±0.3 (X to-6 erg /G2. mole) , xbb P =88.3±0.6, xccP=82.6±0.6; and the anisotropies in the second moments of the electronic charge distribution. By estimating the out-of-plane second moment of the electronic charge distribution as (c 2 )= 4.6±0.4(X 10-16 cml) using free atom values, we have evaluated the remaining individual second moments of the electronic charge distribution to be (a 2 )=21.1±0.6(XlO-lS cm2) and (b 2 )=6.6±0.S. The diagonal elements of the diamagnetic and total magnetic susceptibility tensor also follow from the above estimation of (c 2 ) and are xaa d =-47.5±2.5(XlO-S erg/G2.mole) , Xbb d =-to9.1±3.0, xcc d =-117.6±3.4, Xaa= -1.7±2.S, Xbb= -20.8±3.1, and Xcc= -3S.0±3.S, giving the bulk magnetic susceptibility as x=Hxaa+ Xbb+Xcc) = -19.2±1.8(X 1~ erg/G2.mole). These values are then compared to those of the oxygen analog, formaldehyde, and trends in this pair are compared to several other previously studied oxygensulfur analogs.
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