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Heat capacities of a molecular mixed-ligand complex [Zn(hfac)2(tmen)] were measured in the temperature range between 13 and 383 K with an adiabatic calorimeter and the proton magnetic spin–lattice relaxation times (T1, T1ρ and T1D) were measured in the range between 130 and 330 K, where hfac and tmen denote hexafluoroacetylacetonato and N,N,N′,N′-tetramethylethylenediamine, respectively. The orientationally disordered crystalline phase, designated as phase I, was found to appear only in the supercooled meta-stable state: The temperature, enthalpy and entropy of the fusion were Tfus=(370±1) K, ΔfusH=(2.2±0.1) kJ mol−1 and ΔfusS=(5.8±0.3) J K−1 mol−1, respectively. The small entropy was discussed in relation to the low globularity in the shape of the complex molecule. High- and low-temperature stable crystalline phases (II and III) were found: The temperature, enthalpy and entropy of the fusion from the phase II were Tfus=(375±1) K, ΔfusH=(24.32±0.02) kJ mol−1 and ΔfusS=(65.4±0.1) J K−1 mol−1, respectively. The temperature, enthalpy and entropy of the III-to-II phase transition were Ttrs=(293.8±0.1) K, ΔtrsH=(4.115±0.005) kJ mol−1 and ΔtrsS=(14.02±0.02) J K−1 mol−1, respectively. Glass transitions were found at Tg=(114±1) K in phase III and at Tg=(116±1) K in the supercooled metastable phase II, respectively, and interpreted as attributed to the freezing-in of the rearrangement motion between δ and λ conformations of tmen. The energy difference between the two conformations was less than 0.25 kJ mol−1, and the activation energy for the conformational change was Δea=(33±1) kJ mol−1. The activation energy for the C3 reorientation of methyl groups within the ligand tmen was Δea=(14±1) kJ mol−1.

An anionic motion in sodium thiocyanate was studied by the spin-lattice relaxation time measurements of 14 N nuclear quadrupole resonance. The relaxation time decreased rapidly obeying an Arrhenius equation above T = 375 K. This result suggests the onset of a head-tail reorientational motion of thiocyanate ion with an activation energy of ≈ 95 kJ mol −1 . The origin of an anomalous temperature dependence of the quadrupole coupling constant is reinvestigated in relation to the anionic motion. It is concluded that a gradual change in electronic state of the anions, not the anionic motion, in the crystal with varying temperature is responsible for the anomaly claimed previously. Intermolecular interaction between N and Na atoms is suggested to be the most important factor in the origin of the change in the electronic state of the anion.

A deuteron magnetic resonance study was made on four compounds with an O—D···O hydrogen bond of different strengths. The deuteron quadrupole coupling constant eqQ, asymmetry parameter η, and the directions of the field gradient tensor were determined. The eqQ and η obtained are: KDCO3154.4±0.6 kc/sec,0.194±0.018,(COOD)22D2O D1(water)230.3±2.0 kc/sec,0.062±0.006,D2(water)219.1±2.0 kc/sec,0.16±0.03,} (at−70∘C) D1 and D2121±3 kc/sec,0.93±0.02,(at 67∘C) D3(carboxyl)139.2±0.8 kc/sec,0.098±0.005,ND4D2PO4 (acid D)119.6±0.8 kc/sec,0.053±0.008,K, D−maleate 56.0±0.8 kc/sec,0.53±0.07.The results are discussed in relation to the crystal structure in each case. It was found that the oxalic acid dihydrate crystal used was a new modification, different from the ordinary one. Reorientational motion of a water molecule similar to that in other hydrated crystals was observed in oxalic acid dihydrate from the measurement at different temperatures. A barrier to this motion of 10.0 kcal/mole was determined from the te...

A deuteron magnetic resonance study has been made on a single crystal of urea-d4. At room temperature deuteron quadrupole coupling corresponding to a stationary molecule is obtained. The eqQ and η values determined are: eqQ⁄h=210.8±1.0 kc./sec. and η=0.139±0.010 for D1, and eqQ⁄h=210.7±1.0 kc./sec. and η=0.146±0.010 for D2 at room temperature, and eqQ⁄h=206.3±1.2 kc./sec., η=0.138±0.010 for D2 at 117°C. In both cases the maximum field gradient component and the N–H direction are in good agreement. The onset of reorientational motion about the C=O bond of a whole molecule has been concluded from the line-width change at high temperatures. Above 110°C the effect on the line-width of the reorientation about C–N bond has also been observed. The barrier heights for these motions are estimated to be 11±2 kcal./mol. for the reorientation about the C=O bond and 15±3 kcal./mol. for that about the C–N bond. The temperature dependence of the quadrupole splitting and that of the dipole coupling between 14N and D have...

The temperature dependence of the dipole moment was investigated on monochloromethyl ether (I), sym-dichloromethyl ether (II) and monobromomethyl ether (III) in the gaseous state, and (III) and sym-dibromomethyl ether (IV) in heptane solution. The moment of (I), (II) and (IV) increases with temperature, while that of (III) does not. From the observed data the energy difference between the gauche and the trans position is 0. 7 kcal./mol. in (I), and zero in (III) Similarly ΔE’s between t,g- and g,g-form of (II) and (IV) are estimated to be 1.3 kcal. and obtained to be 0.9 kcal./mol. respectively from the observed results.

The dipole moments of propargyl chloride, bromide and monochlorobutyne in the gaseous state are measured to be 1.65D,1.52D and 2.17D respectively. The moment of propargyl chloride and bromide are considerably smaller than the saturated one even though the correction of C≡C—C skeletal moment is taken into account. This is consistent with the —CH2Cl group moment of dichlorobutyne obtained in the preceding work. These results are inconsistent with the resonance scheme presented by Pauling et al. for propargyl halide. The anomaly is considered as a characteristic feature of the molecules having triple bonds of this kind. By taking all of the moments of dichloro- and monochlorobutynes and propargyl chloride into account, the bond moments, the induction moments and the direction of the resultants, are predicted as shown in Fig. 1.

The dipole moment measurement was made at various temperatures on ethyl, i-propyl and t-butyl nitrites. Observed moments are 2.41D for ethyl, 2.57D for i-propyl, 2.70D for t-butyl nitrite at room temperature. The moment of the latter two compounds decrease slightly with temperature while ethyl compound remains constant. These esters are considered to consist of two isomers: the trans and the cis separated by a barrier of several kcal. due to a resonance effect. The energy difference ΔE between the two isomers is found to be zero in ethyl

The dipole moment of acenaphthene (I) was measured in the gaseous phase as 0.93D. Measurement in benzene solution at 25°C gave the following moment values: acenaphthene (I) 0.85D; 5-chloroacenaphthene (II) 2.50D ; and 5,6-dichloroacenaphthene (III) 3.85D. By the comparison with the moments of naphthalene derivatives it was shown that the moments of (II) and (III) are approximately equal to the sums of the moment of (I) and the moments arising from one and two C–Cl bonds, respectively.