Deguchi, Yasuo

Nishiguchi, Hiroaki

Watanabe, Kohji

Yamauchi, Jun

Kyoto University Research Information Repository

Title Magnetic Properties of 2,2,6,6-Tetramethyl-4-Hydroxypiperidine-1-Oxyl-4-DerivativesAuthor(s)Yamauchi, Jun; Watanabe, Kohji; Nishiguchi, Hiroaki;Deguchi, YasuoCitationBulletin of the Institute for Chemical Research, KyotoUniversity (1973), 50(5): 483-487Issue Date1973-02-28URL http://hdl.handle.net/2433/76456RightType Departmental Bulletin PaperTextversionpublisherKyoto University Bull. Inst. Chem. Res., Kyoto Univ., Vol. 50, No. 5, 1972          Magnetic Properties of 2,2,6,6-Tetramethyl-          4-Hydroxypiperidine-1-Oxy1-4-Derivatives           Jun YAMAUCHI*, Kohji WATANABE*, Hiroaki NISHIGUCHI**                           and Yasuo DEGUCHI***                              Received June 1, 1972    The magnetic susceptibilities of TANOL and 4-substituted TANOL derivatives were  observed in the temperature region from 1.8°K to 300°K. The Weiss constants are deter- mined to be 0°K for methyl and ethyl, —1.5°K for isopropyl and tertbutyl, —1.0°K for  phenyl, —2.5U( for cyclohexyl derivatives, and —6.0°K for TANOL. The temperature, T,,,,  which is proportional to the exchange interaction parameter, J, is roughly estimated to  be 6.5°K for TANOL, 1.5°K for cyclohexyl, and UK for phenyl derivatives. Besides, the 0-H vibration band in infrared absorption spectra was also observed in the radicals where  the hydrogen bond is anticipated to be formed along a crystallographic a-axis. The effect  of the substituents to the exchange interaction was discussed and it is concluded that  the results are not contradictory to the assumption that TANOL may have a linear ex- change interaction along c-axis.                           INTRODUCTION    A number of studies on the magnetic properties of organic free radicals have been performed since the interesting discovery of the magnetic properties of Wurster's blue perchlorate and attention is given to the magnetism of organic neutral radicals. Re-cently, it was confirmed from the susceptibility and specific heat measurements that Galvinoxyl radical exhibits a phase transition of first-order nature at 81.5°K.B On the other hand, the magnetic properties of porphyrexide show an alternating linear chain interaction of Ising type and no phase transition in the temperature range from 1.8°K to 300°K.2) One of the present authors has discussed on the magnetic properties of the organic free radicals in detail and it is concluded that the neutral organic free radicals with one unpaired electron in a molecule have a one-dimensional antiferromagnet-ic spin array with a Heisenberg type isotropic exchange interaction.3) 2,2,6,6-tetra-methyl-4-hydroxypiperidine-1-oxyl (TANOL) is one of the typical model samples which show a linear antiferromagnetic Heisenberg interaction of an isotropic exchange.3'4 The crystal structure, shown in Fig. 1, was determined to be monoclinic and a=7.05A, b =14.08A, c=5.78A, and 0=118°40'.5' The molecules lie along a-axis through a hydro-gen bond to form a linear chain. However, it is difficult to conclude whether the direc-tion of linear exchange interaction is along the direction of hydrogen bonding or along c-axis, where the lattice constant is the shortest. To study the magnetic properties of   * Il1FA] r aC 71 : Laboratory of Solid State Chemistry, Institute for Chemical Re-    search, Kyoto University, Uji, Kyoto.  ** NG 0.10: Faculty of Science, Kyoto University, Kyoto. *** fj!jl]Jc : Faculty of General Education, Kyoto University, Kyoto. (483)                 J.  YAMAUCI-II, K. WA'I'ANABE, H. NiSHIGUCHi and Y. DEGUCIUI           .....1111111111111eir              -- 41111111.11.11111111."":,  'Jill/.'-' C .                                      h. \,4.0B b                                                           a                                      7.05 A 13=118°40'            Fig. 1. Crystal structure of TANOL.......indicates hydrogen bond. TANOL further and the effect of the substituents to the magnetic interaction, we measured the magnetic susceptibilities of TANOL 4-derivatives at low temperature region. The syntheses, ultraviolet and infrared absorption spectra, and electron spin resonance (ESR) spectra of TANOL derivatives have been already reported in this Bulletin. 6,7)                          EXPERIMENTAL    TANOL and its derivatives were prepared through the oxidation of the correspond-ing amine of 4-substituted 2,2,6,6-tetramethyl-4-hydroxypiperidine following the process of Rozantsev.8) Triacetoneamine (I) was reacted with Grignard reagent RM2X and the product was oxidized by hydrogen peroxide as follows. OR OHR OII   II\/\/      I-IC> CC <HRM ,,XHC> CC <I;H202HC> CC <H  HHHHHII    CH3CH3> CH3CI-I3 > CH3C<CH3    CH3--- C<CH3CH3>C C<CH3 CH3>CCH3   \N/\N/\N/ III  HH0          (I) R= —CH3, —C2H„ —CH(CH3)2, -C(CH3)3, -C6H„ -C6H11 The other preparation is the procedure from 2,2,6,6-tetramethyl-4-piperidone-l-oxyl as O0R OI-I  HII\/  ccc     H>C C<HH 202H>CC<HRM6XI-I>C C<H  HHIIIIHH   CH3,, I CH> CH3I I CH3> CHCH    CH3>j>CH3CH3>/>CH3CH3>./<CH3  N/N II  H00 (484)                    Magnetic Properties of TANOL Derivatives The samples were purified by recrystallization and sublimation. The method of synthesis was described in detail in this  Bulletin,6 in which the ultraviolet and infrared absorp-tion spectra were also reported. The susceptibility measurements were done, by means of a magnetic torsion balance,9> on powder samples of about 100-50 mg in a field of 8.8 KOe. The detail of the experiment was also described elsewhere.3)                      RESULTS AND DISCUSSION    The results of the susceptibilitymeasurements of TANOL and its derivatives are shown in Fig. 2. The absolute molar susceptibility was corrected for diamagnetism using Pascal's constants.10 TANOL shows a broad maximum in susceptibility at 6.5°K as is already reported.3,4> On the other hand, the derivatives of TANOL exhibit no broad maximum above the temperature 1.8°K, but obey the Curie-Weiss law, yn1=C/ (T—©), where C and 0 are the Curie and Weiss constants respectively. The Weiss constants are determined to be 0°K for methyl and ethyl, —1.5°K for isopropyl and tertbutyl, —1.0°K for phenyl, —2.5°K for cyclohexyl derivatives, and —6.0°K for TANOL. The susceptibility deviates from the Curie-Weiss law at low temperature region and seems to display a broad maximum at lower temperatures. In TANOL derivatives except methyl and ethyl ones the temperature, T,n, which shows broad maximum in susceptibility, is approximately estimated as in Table 1. Comparing the susceptibility results excepting that of TANOL, the temperature, T,,,, which is pro-portional to an exchange interaction parameter, J, becomes large as the bulky sub-stituent is attached to 4-position of TANOL. It can be presumed that the substituent in 4-position may cause a long distance between molecules along c-axis more than along a-axis, so the exchange interaction in TANOL is reduced by the substituent in 4-posi-tion of TANOL, for, according to the ESR spectra in solutions, the unpaired electron is almost localized on N-O bond and we can regard the electron spin as a localized                4 51 TANOL          32 cyclohexyl H0003 phenyl                                       4 isopropyl        2tertbutyl ° -4005 methyl    y -300ethyl :=1 -200 1 m w —100         ,n J) 1 2 3 4 10 20 30 40 10t I e I I , ,                           TEMPERATURE °K             Fig. 2. Molar susceptibilities of TANOL and its derivatives. (4185)                J.  YAMAUCHI, K. WATANABE, H. NISIIIGUCUI and Y. DEGUCTII                                   Table 1 R0T„OH CKBr) H—6.0°K6.5°K3410 cm-1 CH30--3500*   C2H50—3445** CH(CH3)2 -1.5<13410     C(CH3)3 --1.5<13470 C5145—1.0—13430 C61111—2.51.53380   * R. Briere, H. Lemaire et A. Rassat, Bull. Soc. Chitn. France, 1965 3273.  ** E. G. Rozantsev and M. B. Neiman, Tetrahedron, 20, 131 (1964).                                            I T                    ?     3500 3000 cm-13500 3000 cm' (a)(b)      Fig. 3. OH vibration bands of infrared absorption spectra of TANOL (a) and        phenyl derivative (b). moment. However, the effect of a size of the substituents to the exchange interaction is not explainable, although it is very small. It may be due to the orientation of N-0 bond in the crystal.    The strength of the hydrogen bond along a-axis remains almost same in TANOL and TANOL derivatives. It may be safely said from the broadening of the 0-H vibra-tion in infrared absorption spectra, as shown in Fig. 3, that the substituents have little effect to the crystal structure along a-axis, which is consistent with the presumption mentioned above. In conclusion our present results are not contradictory to the assump-tion that the TANOL radical may have a linear exchange interaction along c-axis, although the absence of the crystallographic data of TANOL derivatives does not reveal the situation clearly. We are now engaged in the experiment of the crystallographic analysis and the susceptibility measurement at lower temperatures. (436 )                   Magnetic Properties of TANOL Derivatives                          REFERENCES (1) K. Mukai, Bull.  Chem. Soc. Japan, 42, 40 (1969), A. Kosaki, H. Suga, S. Seki, K.     Mukai and Y. Deguchi, ibid., 42, 1525 (1969). (2) T. Fujito, H. Nishiguchi, Y. Deguchi and J. Yamauchi, ibid., 42, 3334 (1969). (3) J. Yamauchi, ibid., 44, 2301 (1971). (4) J. Yamauchi, T. Fujito, E. Ando, H. Nishiguchi and Y. Deguchi, J. Phys. Soc. Japan,     25, 1558 (1968), Yu. S. Karimov, JETP Lett., 8, 145 (1968), J. Yamauchi, T. Fujito,      H. Nishiguchi and Y. Deguchi, Proceedings of 12th Inter. Conf. Low Temp. Phys.,     Kyoto, 805 (1970). (5) Lajzeronicz-Bonneteau, Acta Cryst., B24, 196 (1968). (6) K. Watanabe, J. Yamauchi, H. Takaki, H. Nishiguchi and Y. Deguchi, Bull. Inst. Chem. Res., Kyoto Univ., 48, 88 (1970). (7) K. Watanabe, J. Yamauchi, H. Takaki, H. Nishiguchi and Y. Deguchi, Bull. Inst.     Chem. Res., Kyoto Univ., 48, 264 (1970). (8) E. G. Rozantsev, Izv. Akad. Nauk SSSR, ser. Khim., 12, 2218 (1964). (9) M. Mekata, J. Phys. Soc. Japan, 17, 796 (1962). (10) P. W. Selwood, "Magnetochemistry" Interscience Publisher, New York (1956). (487)

Magnetic Properties of 2,2,6,6-Tetramethyl-4-Hydroxypiperidine-1-Oxyl-4-Derivatives

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Magnetic Properties of 2,2,6,6-Tetramethyl-4-Hydroxypiperidine-1-Oxyl-4-Derivatives

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