from eq. 2 using k and estimates of Bo.6) To separate the dipole moment, pO2, from Aa, the change with wave length of A a was estimated from the curves of Figure 1 and divided into the corresponding change in AapOz2 to obtain estimates of 120 and 70 D. ( f 2 0 % ) for the permanent moments of met-and oxyhemoglobin, respectively. The shape effect contribution was then estimated as about -40 X ml. for both molecules. It is unlikely that an intrinsic anisotropy of static polarizability could lead to an orientation parallel to the short axis of the magnitude observed. If there is a mechanism favoring orientation parallel to the long axis of the molecule, such as anisotropy in a fluctuation dipole or in an ion-atmosphere polarization, the above analysis would then yield only a lower limit to the permanent dipole along the twofold axis. From this possibility it can be seen that if the data had suggested case a, no inference about the existence of a permanent dipole could have been made. Calculations of the electric dichroism suggest that no signal should have been observed for case b and the amount of orientation predicted by the Kerr effect, so that this experiment was consistent with the interpretation of the Kerr effect measurements.It is therefore reasonable to conclude that the above experiments and analysis are evidence for a permanent dipole along the twofold axis in hemoglobin at neutral pH. The suggestion of a greater dipole moment for methemoglobin relative to oxyhemoglobin is consistent with the dielectric increment data,* although dipole moments estimated from dielectric increments (400-500 D.) apparently include contributions that are not effective in orientation, such as a randomly oriented fluctuation dipole or an ion-atmosphere polarization about an almost spherical molecule.

Amorphous boron nitride, BN, is obtained from the reaction of B-trichloroborazine, (BCINH)(3), with cesium metal. The amorphous product is converted to a turbostratic form upon heating to 1100 degrees C. Scanning electron microscopy reveals a previously unreported morphology composed of hollow tubular structures. The largest of these appear to be approximately 3 micrometers in external diameter and 50 to 100 micrometers in length. Transmission electron microscopy and selected-area electron diffraction also indicate the tube walls to be turbostratic in nature. The mechanism by which the tubes form is not known, although apparent sites of incipient tube growth have been observed.

The structures of n-B18H22 and of n-B18H22 x C6H6 were determined by single-crystal X-ray analysis at -60 degrees C. The geometry of the boron cluster itself does not seem to be appreciably affected by solvation. There does, however, appear to be an unusual interaction of a polyborane bridging hydrogen atom with the benzene pi system, giving rise to an extended stacked structure. The 1H{11B} spectrum of n-B18H22 in [D6]benzene differs from that in [D12]cyclohexane most noticeably in the bridging proton region. Upon moving from the aliphatic to the aromatic solvent, the greatest increase in shielding was for the signal corresponding to the bridge hydrogen atom that interacts with the pi system of benzene; the signal was shifted upfield by 0.49 ppm. Density functional theory calculations were performed on 1:1 and 2:1 complexes of the n-B18H22 unit with benzene.

The structure of [PPh(3)(benzyl)][B(10)H(11)] was determined at -123 degrees C and 24 degrees C by single-crystal X-ray analyses. The B(10) core of [B(10)H(11)](-) is similar in shape to that of [B(10)H(10)](2)(-). The 11th H atom asymmetrically caps a polar face of the cluster and shows no tendency for disorder in the solid state. Variable temperature multinuclear NMR studies shed light on the dynamic nature of [B(10)H(11)](-) in solution. In addition to the fluxionality of the cluster H atoms, the boron cage is fluxional at moderate temperatures, in contrast to [B(10)H(10)](2)(-). Multiple exchange processes are believed to take place as a function of temperature. Results of ab initio calculations are presented. Crystal data: [PPh(3)(benzyl)][B(10)H(11)] at -123 degrees C, P2(1)/c, a = 9.988(2) A, b = 18.860(2) A, c = 15.072(2) A, beta = 107.916(8) degrees, V = 2701.5(7) A(3), Z = 4; [PPh(3)(benzyl)][B(10)H(11)] at 24 degrees C, P2(1)/c, a = 10.067(5) A, b = 19.009(9) A, c = 15.247(7) A, beta = 107.952(9) degrees, V = 2775(2) A(3), Z = 4.