Bassiouni, M E

EL-Shamy, F

Gaafar, M

Mahmoud, I

IACS Institutional Repository

Indian J. Phys. 69A (5), 553-559 (1995)IJP A— an international journalDiamagnetic anisotropy and molecular structure of succinimide derivativesM Gaafar, M E Bassiouni, F EL-Shamy and I Mahmoud Deportment of Physics, Faculty of Science, Alexandria University, EgyptReceived 5  October 1994. accepted 18 May 1 995Abstract : The axial diamagnetic susceptibilities of succinimide C4H5NO2 and its derivatives i.e isomorphous pair C4H4NO2X (X = Cl, Br). were measured and their molecular values were deduced using the molecular tensor relations These measurements show chat each of these crystals has unique magnetic axis and the molecular plane in succinimide compound lies nearer to (001) plane but in each of its derivatives lies in the vicinity of (010) plane Effect of substitution of chloride and bromide 10ns on the magnetic anisotropy of these isomorphous pair were studied. Correlation between these results and other physical properties of these moleculur crystals, providing acceptable information on their molecular structure, was established. Effect of the packing forces in these crystals was also discussedKeywords : Diamagnetic anisotropy, molecular structure, succinimide derivatives PACS Nos. : 75.20.Ck, 75.40.CxStudy o f the physical properties o f  molecular crystals having similar structure may be important to give valuable information on the general features o f  their structures [1 -3 ]. Only in a few cases, this information could be obtained directly from X-ray data. In some other cases, the ’trial and error' structure has been obtained by an intensive study o f the X-ray data which is a difficult problem involving much time and labour. Any independent physical methods which indicate the approximate configuration and orientation o f the m olecules in the crystal are therefore greatly welcomed. Fortunately, crystal structure of the present heterocyclic succinim ide and its derivatives i.e. isomorphous pair N-chloro and N-bromo succinim ide, are known [4,5]. The general structural formula o f them is shown in Figure 1.Succinim ide crystal is orthorhombic 14] and the structure is built up through the usual Van der W aals forces. The crystals o f  isomorphous pair N-chloro and N-bromo succinim ide are also orthorhombic [5] and their m olecules are significantly planar. The©  1995 1ACSpresent w ork is devoted  to provide m ore in form ation on the m olecu lar  structure o f  these  m olecu lar crysta ls and to investigate  the e ffec t o f  ha logen  substitu tion on  their d iam agnetic  an isotrop ies.554 M  Gaafar, M E Bassiouni, F El-Shamy and / Mahmoudo  N ocIC H 2Figure 1. Structural formula of succimmidc and its N-chloio and N-bromo succimmide derivatives. C4H4N 0 2X (where X = H. Cl. Bi) jX /S u cc in im id e  cry sta ls  are grow n  from  a so lu tion  o f  su cc in im id e  in m ethyl ethyl ketone and larger crystal are grow n by seed in g  the so lu tion . THc density  p a n d  m olecu lar  w e ig h t M  are 1 .4 2 5  g / c i r f  and 9 9  m o l. r e sp e c tiv e ly . N -C h lo ro  su cc in im id e  crystal C 4 H4 Q 2CI (N C S ) are obta ined  from  its so lu tion  in b en zen e  by slo w  evaporation  as sm all tabular p lates. T his com poun d  has p =  1.66 g /cm 3 and M -  138.5 m ol. C rystals o f  N -brom o  su cc in im id e  C 4 H iQ 2Br (N B S ) are obtained from  so lu tion  in benzene as thin p lates. The m eth od  o f  m easu rem en t used  in the determ ination  o f  the m agnetic  an isotrop ies o f  these  cry sta ls , has been m en tion ed  e lsew h ere  [6 ,7 ]. In this m ethod, lh^ crystal w as suspended  a lon g  o n e  o f  its principal ax es by very fine quartz wirfi at the centre o f  a uniform  m agnetic  fie ld  to avoid  any co m p lica tion s due to lateral forces acting on the crystal. The upper end ol the fin e  quartz is attached to the cen ter o f  a graduated torsion head w h ich  w as used to m easure the tw istin g  a n g le  o f  the fibre quartz at the balanced point betw een  the restoring  c o u p le  due to the fie ld  and the crystal anisotropy. M easurem ents w ere perform ed on sm all crysta ls , w e ig h in g  0 .2  and 0 .8  m g. In all cases, m easurem ents w ere carried out on each o f  these  crysta ls in at least three different orientations in order to calcu late  the crystal m agnetic  an iso tro p ies and to com pare the ca lcu lated  and ob served  values. E ach crystal w as a lw ays  w eig h ed  accu rately  just before and after the m agnetic m easurem ents, in order to detect any v o la tiliza tio n  o f  the crystal due to its rapid rotation during the exp erim en t and lo ss  o f  w eig h t su b seq u en tly  check ed . _S tu d y  o f  d ia m a g n e t ic  s u s c e p t ib il i ty  o f  o r th o r h o m b ic  c r y s ta ls  l ie s  in the determ ination  o f  the crystal an isotropies, thus .X a - X „  =  A  1 a ~ X c =  B  Jw h ere  A  and B  arc the an isotropy va lu es w h en  the crystal is susp en ded  a long  c -a x is  and &-axis resp ectiv e ly . M aking  use o f  the relationX a +  X„  +  X c =  C. (2)D iam agnetic an isotropy and  m olecular structure etc 555w here %M =  C /3  is  the gram  m olecu lar su scep tib ility  m easured by G ouy pow d er m ethod  [8], the v a lu e s  o f  x a * Xh'  X c are deduced as fo llo w s :X a =  | ( / 4  +  / J + C )X h =  ~ j A  +  j ( B + C ) (3 )Xt = -\b + ^ (A  + C)T h e re la tion s b etw een  the axia l d iam agn etic  su scep tib ilit ie s  x a ' Xh'  X c aiu* the  m olecu lar  d iam agnetic  su scep tib ilities K h  K Mt K N [9] are g iven  by :X a =  ^ L a i +  a 2 +  K n  <*3xh =  k l p f  +  K m P 2 +  K N P l  (4 )= k l yl + y\ + y\w here a 2 , /J2 , y 2 (i =  1^ 2 , 3 ) d enote  the sum m ation o f  the d irection  c o sin e s  w h ich  is taken o v er  all the in d ep en d en tly  oriented  m o le c u le s  in the unit c e ll. From  eq. (4 ) , them olecu lar  su scep tib ilitie s  are as fo llo w s :xu al « 2 al* / .  = xh Hi Hi Hi HixL y\ r ,2 yl yl yl-l Xa °l <x\ « ,2= Hi X h Hi Hi Hiyl X L /.I r ? yl yla ? «l a ; al al* *  = Hi -K Hi Hi Hiyl r 2 yl y\ ylSubstitu ting for x a - X h* £ r fpom e 9- ( 3 )» w e SetK l = j [(a ,-2A ,+c,)/4  -  (a ,+ fc ,-2 c ,)fl + (a,+fc,+c,)C ],K" = J5 [ ^ ~ 2b2+c2^ A ~ (a2+fe2-2c2)fl + (a2+fr2 + c2)C], (5)~  [(a, -2 6 3 + c3)A -  (fl3 + 63-2cj)£> + (aj + Aj+CjJC],and556 M  Gaafar, M E  Bassiouni, F  El-Shamy and l  Mahmoudw here «, -  firl - Plrl = Plrl - Phi =  Phi ~ Plrlb\ = rl«l - rial, b 7 =  r i a l  -  r i a l ,  bi = rial -  rial,T he m olecu lar d iam agnetic  anisotropy is g iv en  by the relationc, = a \p l -  a lp l - c2 = a l p f  -  a l P l ,  c3 = a l P l  -  af t2.AK  = K n2 (6)T h e m easured  axial d iam agn etic  a n iso trop ies o f  su cq in im id e and its isom orphous  pair deriva tives are listed  in T able 1.Table 1. Axial diamagnetic anisotropies ( lO^cmVmole)Crystal Axial unisotropy \X b -X a X c"X o X t- X bS + 6.2 7 1 + 0 9NCS - 7  1 - 0 6 + 6.5NBS - 7  2 0 9 + 6 3T o  get the v a lu es  o f  the crystal d ia m agn etic  su scep tib ilit ie s  x ti' Xb'  X C' fo llo w in g  relation w as usedxM = \[xa + xh + x,\w here x M has been m easured several tim es by fam iliar G ouy m ethod. T he results are listed  in T ab le  2.Table 2. Axial diamagneitc susceptibilities (10“6 cmVmole)CrystalAxial diamagnetic susceptibilities Mean valueTLmXo Xb XrS 56.3 ~  50 1 49.2 51.9NCS 58.2 65.3 58.8 60.8NBS 68.3 75.5 69.2 71.0M a x im u m  d ia m a g n e tic  su sc e p t ib ility  ( & )  a lo n g  [1 0 0 ]  d ir e c t io n  and sm all d ia m a g n etic  an isotropy ( Xb ~ X c )  *n (1 0 0 )  p lane, ind icate that the S crystal is m agnetically  u n iax ia l a lo n g  [1 0 0 ] d irection  and the m o lecu lar  p lan e is nearer to  (1 0 0 )  p lan e. For the o th er  tw o  ism orp h ou s pair (N C S ) and (N B S )  crysta ls , larger Xh a lo n g  [0 1 0 ] d irection  and sm a ll ax ia l d iam agn etic  an isotrop ies in (0 1 0 )  p lane, w ere obtained. T h ese  results, sh o w  that th ese  crystal are m a g n etica lly  un iaxial a lo n g  [0 1 0 ] d irection  and the m olecu lar  p lane is inDiamagnetic anisotropy and molecular structure etc 557the v ic in ity  o f  (0 1 0 )  plane. It is clear that the substitu tion  o f  H  ion  in S crystal by C l or Br  ion, lea d s to  the rotation  o f  the m olecu lar  p lan e from  the v ic in ity  o f  (1 0 0 )  p lane to the  neighborhood o f  (0 1 0 )  p lane, w h ich  in turn a ffect the ph ysica l properties o f  these  m olecu lar  crystals. M easurem ents o f  the optical anisotropies [10J and the X -ray investiga tion  o f  these  crystals [4 ,5 ] sh o w  that the m olecu lar  p lan e is in the v icin ity  o f  (1 0 0 )  plane in su cc in im id e  and o f  (0 1 0 )  p lane in its d erivatives w hich in turn, support the present results. T he va lues o f  the sm a ll in c lin ed  a n g le s  o f  m olecu lar p lan es o f  these crysta ls h ave  been d iscu ssed  later. The ca lcu la ted  d irection  co sin es  a „  j3„ jj (1 =  1, 2 , 3) o f  the m olecu lar axes L , M , N  referred  to the a x es a* b , c>  are g iven  in T able 3.Table 3. Direction cosines of L, M, N  referred to o, b, t .CompoundDirection cosinesi«i A 7iS 0 7823 -0.1889 0.5940 30.6282 0.0187 0.7778 2-0.1360 0.9836 0.1184 1NCS & NBS 0 4732 0.8783 0.0675 30.8062 0.3987 0 4370 20.3569 0.2612 -  0.8967 1L  is taken parallel to the length  o f  the m o lecu le , M  is norm al to  L  in the m olecu lar  p lan e  and N  is  norm al to the m o lecu la r  p lan e as sh ow n  in F igu re  1. T h e  m o lecu la r  d ia m a g n etic  su sc ep tib ilit ie s  K l , K m, K n and the an isotropy A K  w ere ca lcu la ted  usin g  eqs. (5 )  and (6 ) resp ectively . T he results are g iven  in T able 4.Table 4. Molecular diamagnetic susceptibilities and anisotropies ( I0~* cmVmole).CompoundMolecular diamagnetic susceptibilitiesAnisotropy (AK)Kl Ku k nS 50.0 40.6 63.9 18.15NCS 59.1 52.6 73 9 18.05NBS 72.0 59.9 84 3 18.35N o w , after the ca lcu la tion s o f  the m olecu lar d iam agnetic  va lues, it is easy  to get the orientational a n g les o f  the m olecu lar p lanes from  the relation :X a =  s in 2 0  +  K ± c o s2 9= jr, + (* ,.-* „) cos2 eX h =  * ,  +  ( * ! - * , )  c o s 2 0 .andw here *  ( K L +  K M ) / 2  and K ± =  K N >For S  co m p ou n d , 0  «  41° and for N C S and N B S , 0  »  4 3 .7 ° .T he c o in c id en ce  o f  the m axim um  value o f  the m olecu lar  d iam agnetic  su scep tib ility  in the norm al d irec tio n  o f  the m o lecu la r  p lan e  w ith  the m in im u m  m o lecu la r  optica l refractiv ity  for these  crysta ls, ind icates that the m o lec u le s  are planar. X -ray  investigation  [4 ,5 ]  in d ica tes id en tica l resu lts . T h e nearly  eq u a l v a lu e s  o f  a n iso tro p y  A K  o f  these  m olecu lar crystals, su g g est the sam e packing forces in them  [11]. M agnetic  contribution o f  b on ds (C -B r ) , (C -C l)  w ere ca lcu la ted  re la tiv e  to su cc in im id e  m o lec u le , the resu lts are listed  in T ab le  5. ,558 M Gaafar, M E Bassiouni, F El-Shamy and /  MahmoudTable 5. Diamagnetic contribution of (C-X) bonds relative to S molecule (10”6 cmVmole)BondMolecular components*„ K±C-Br 10 1 10 0C-CI 21.2 20.9\T h ese  results sh ow  that the substitu tion o f  H ion  by halogen  ion  leads to  an increase  in the v a lu e  o f  the d ia m a g n etic  su sc ep tib ilit ie s  in Jhe p lan e o f  the m o lec u le . It is a lso  n o ticed  that the su bstitu tion  by brom ide ion in creases the d ia m a g n etic  su sc ep tib ilit ie s  further, as com pared  to that o f  ch loride ion due to the d ifferen ce  o f  the spreading e ffe c t o f  their e lectron  c lo u d s [2].T h ese  m casurm ents ind icate that these crystals are m agnetica lly  uniaxial a long  [100] d irection  w h ich  is  the a x is o f  sym m etry  in S crystal w hereas it is a lo n g  the [0 1 0 ] a x is in N C S  and N B S  cry sta ls . T h e  m o lecu la r  p lan e  is in c lin ed  to (1 0 0 )  p lan e  by 4 1 °  in  S com p o u n d  and by 4 3 .7 °  to (0 1 0 )  p lane in its d erivatives N C S and N B S . T h ese  results show  a lso  that the substitu tion  by h a logen  ions rotates the m olecu lar  p lane from  the v ic in ity  o f  (1 0 0 )  p lan e  to  that o f  (0 1 0 )  p la n e  and in crea ses the d ia m a g n etic  su sc ep tib ility  in the m o lecu la r  p lan e  by d ifferen t v a lu es due to the d ifferen ce  o f  the spreading e ffe c t  o f  their e lectron  c lo u d s. T he nearly equal va lu es o f  A K  su g g est equal va lu es o f  p ack in g  fo rces in these  crystals.References[1] E Manghi, C A De Caroni. M De Benyacor and M J De Abeledo Acta Cryst. 33 205 (1967)[2] M Gaafar, M A Las been. A A Ali and A M Ahmed Phys. Star. Sot. K259 (a) 111 (1989)[3] M Gaafar and M El-Shobosy Fiiika A3 193 (1994)[41 R Mason Acta Cryst. 9 405 ( 1956)[5] R N Brown Acta Cryst. 14 711 (1961)Diamagnetic anisotropy and molecular structure etc 559[6] K  S Krixhnan and S Banerjee Phil Trans, A234 26.*> (1935)[7] M  A  Lushcen Pli.D. Thesis (University College. London) (1952)[8] A  Eamshaw Introduction to Ma/tnetochenusiry (London : Academic) (1968)[9] K  Lonsdale and K  S Knshnan Prim. Roy, Soc. AI56 597 (1936)110] M  Caal'ar. T  G  Abd EI-MaliL. M  El-Shabasy and I Mahmoud Indian J. P irn . 65A 318 (I99h |ll] K Lonsdale and E W  Toor Arm Cryst. 12 1048 (1959)

Diamagnetic Anisotropy and Molecular Structure of Succinimide Derivatives

http://arxiv.iacs.res.in:8080/jspui/bitstream/10821/4831/1/Diamagnetic%20Anisotropy%20and%20Molecular%20Structure_By%20M%20Gaafar.pdf

Diamagnetic Anisotropy and Molecular Structure of Succinimide Derivatives

Abstract

Similar works

Full text

Available Versions

IACS Institutional Repository