A C T A U N I V E R S I T A T I S L O D Z I E N S I S _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ FOLIA CHIM CA 8, 1988_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
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Joan na M a s ł o w s k a , G r z e g o r z Bazy lak
NICKEL (II) SCHIFF RASE C O M P L E X E S AS S T A T I O N A R Y PHAS ES IN GAS C H R O M A T O G R A P H Y “
The p o s s i b i l i t y of s e p a r a t i n g some alka nes or a l c o h o l s m i x ture by gas c h r o m a t o g r a p h y in a p a c k e d c o l u mns with t e t r ade nt a- te Schiff base nickel (II) c o m p l e x e s has been studied. The e f fects of m o d i f i c a t i o n in the c h e l a t e s t r u c t u r e on the colu mn s e l e c t i v i t y are p r e s e n t e d c o m p a r i n g the a p p r o p r i a t e heat s of a d s o r p t i o n .
It is now well e s t a b l i s h e d that the Schiff base c o m p l e x e s of the n u mb er tr a n s i t i o n metal ions c o ul d be s u c c e s s f u l l y e m p l o y e d as liqu id [ l , 2] or solid [3] phas es for the gas c h r o m a t o g r a p h i c (GC) s e p a r a t i o n of a wide range of solutes. Ho wever, in these re po rts the nickel (II) c o m p l e x e s with b i d e n t a t e [ l , 2] or t e t r a d e n t a t e [3] s u b s t i t u t e d s a l i c y l a l d i m i n a t e s were only used. In the p r e l i m i n a r y s t u d i e s [4] we n o te d that the ne ut ral nick el (II) c h e l a t e s of the t e t r a d e n t a t e Schi ff bases, de ri v e d from Ji-diketones and a p p r o p r i a t e di amines, co uld be a p p l ied as the c o m p o n e n t s of in t i m a t e l y m i x e d GC s t a t i o n a r y phases. It was r e p o rte d [5] that the c o o r d i n a t i o n g e o metry, thermal s t a b i l i t y and v o l a lit y of such c h e l a t e s had many su p e r i o r feat ure s than th ose of the p r e v i o u s l y used in GC. T h e r e fore, in p r e s e n t paper, a range of nick el (II) c h e l a t e s c o n t a i n i n g c e r t a i n m o d i f i c a t i o n s to the ligand s t r u c t u r e are be ing c o m p a r e d in terms of s e p a r a t i o n e f f i c i e n c y to wa rds a l i p h a t i c h y d r o c a r b o n s and alcohols. On the basis of some t h e r m o d y n a m i c data it was i n t e r e s t i n g to in v e s t i g a t e the d i s t i n c t i o n in such GC c o l u mns s e l e c t i v i t y what can be ap pl ied for the o p t i m i z a t i o n of the s o r b e n t s c o m p o s i t i o n in GC.
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I n s t itu te of Fu n d a m e n t a l Food Ch em ist ry , T e c h nic al U n i v e r s i ty of Ł ódź.
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E x p e r i m e n t a l
M a t e r i a l s
All c o m p l e x e s see (Tab le 1) w e re s y n t h e t i z e d , p u r i f i e d and c h a r a c t e r i z e d a c c o r d i n g to m e t h o d s d e s c r i b e d p r e v i o u s l y [6, 7]. As the s o r b a t e s the al ka n e s and a l c o h o l s were used, all in a n a l y t i c a l re ag e n t grade.
T a b l e 1 Schi ff base nickel (II) c h e l a t e s s t u d i e d
No Sy s t e m a t i c name A b b r e v i a t i o n M o l . w t . 1 N , N ’- e t h y l e n e b i s ( a c e t y 1 a c e t o n e i -
mi n e )Ni (II) Ni ( e n ) A A 282.28
2 N N - t r i m e t y l e n e b i s ( a c e t y l a c e t o n e i -
m i n e )Ni (II) N i (tm)AA 296.30
3 N N - o r t o - p h e n y l e n e b i s ( a c e t y l a c e - t o n e i m i n e ) N i (II) N i ( p h ) A A 334.68 4 N N - e t h y l e n e b i s ( b e n z o y l o a c e t o n e i - mi n e )Ni (II) Ni ( e n ) B A 405. 10 5 N N - t r i m e t y l e n e b i s ( b e n z o y l o a c e t o - ne i m i n e ) N i (II) N i ( tm)BA 419. 12 6 N N - o r t o - p h e n v l e n e b i s ( b e n z o y l o a c e - t o n e i m i n e ) N i (II) Ni ( p h ) B A 457.50 Gas C h r o m a t o g r a p h y
A mode l 504 gas c h r o m a t o g r a p h ( M e r a -E lw ro , Wr ocław, Poland) e q u i p p e d wi th a flame i o n i z a t i o n d e t e c t o r and a m o de l K B 5 5 0 3 d i gital i n t e g r a t o r (Kabidez, Warsaw, Po la nd) was used. The s t a i n l e s s steel co lumns, 1.3 m x 0.4 cm i.d., p a c k e d wi th 18% of the a p p ro p r i a t e nick el (II) ch el a t e on C h r o m o s o r b W NAW, 8 0 /1 00 mesh, w e r e used in all in st anc es . The a m o u nts of c h e l a t e d e p o s i t e d on the s u p p o r t were c h e c k e d t h e r m o g r a v i m e t r i c a l l y by u s in g the de- r i v a t o g r a p h of P a u l i k - P a u l i k - E r d e y s y s t e m (MOM, Bu da pes t, Hu ngary). The a d s o r b e n t s were h e a t e d in the n i t r o g e n a t m o s p h e r e w i t h the he a t i n g rate 5 °C/min.
The GC m e a s u r e m e n t s w e re m a de i s o t h e r m a l l y at 100, 120 and 135 + 0.1 °C. H e l i u m was used as the c a r r i e r gas and the c o n s t a n t
flow rate, 40 ml/min, was ma nt ain ed . The so lu t e s we re in je cte d as di lu t e d vapours by use a 10 pi g a s - t i g h t syringe, what caus ed that s y m e t r i c and samp le size (1 : 20) in d e p e n d e n t pe aks were o b tained. At such low c o v e r a g e of the a d s o r b e n t s s u r f a c e the heats of a d s o r p t i o n were d e t e r m i n e d from the slop es of lnt^ vers us 1/T (c ol umn te mp e r a t u r e ) plot s [8]. A d j u s t e d r e t e nti on times tA of
rv the so lu tes st ud ied were d e t e r m i n e d by Et tre m e t h o d [9].
Re su lts and O i s c u s s i o n
The nickel (II) c o m p l e x e s s t u d ied diff er in the h y d r o c a r b o n b r id ge c o n n e c t i n g the two n i tr oge n do nor atoms and in the phenyl s u b s t i t u e n t on the c a r b ony l grou ps in the ligand moiety (see Figure 1). Both of these s u b s t i t u t i o n pr od u c e the ch an g e s in po la rity, m a g n e t i c and Lewi s a c i d -ba se p r o p e r t i e s of these planar, c o o r d i n a t i v e l y u n s a t u r a t e d c h e l a t e s [10].
R “
-C H 2-C H 2-
R1= “ CH3
-C H 2-C H 3-C H 2-
-P h
&
H
Fig. 1. S t r u c t u r e of the c h e l a t e s st ud ied
The heats of a d s o r p t i o n d e t e r m i n e d for n o n - s p e c i f i c a l l y i n t e r a c ti ng al ka nes and for s p e c i f i c a d s o r b a t e s are list ed in Table 2 and 3. Un der the c o n d i t i o n s e m p l o y e d the l i ne ar r e l a t i o n s hips b e t w e e n he ats of a d s o r p t i o n and the total n u mb er af carbon at oms in the m o l e c u l e of h o m o l o g o u s series of the s o r b a t e s were observed. In Table 4 the best fit re g r e s s i o n data for these f u n c tions are given. The resu lts d e m o n s t r a t e that he ats of a d s o r p t i o n in c r e a s e d with resp ect to the h y d r o c a r b o n b r id ge in the nick el (II)
T a b l e 2 He ats of a d s o r p t i o n (-AH) of n - a l k a n e s
on the c h e l a t e s st ud i e d
Solu te
S t a t i o n a r y ph ase
Ni (e n)A A N i ( t m)A A Ni ( p h ) A A N i (en)BA N i ( t m ) B A N i ( p h ) B A ( - A H ) ( k c a l / m o l ) Pe nt a n e 2.42 2.51 3.20 3.75 3.96 4.03 Hexa ne 2.73 2.89 3.55 4.50 4 .88 5.10 He pt a n e 3.10 3.35 3.90 5.24 5.79 6 .18 Octa ne 3.40 3.81 4 . 30 6.01 6.70 7.31 Nona ne 3.73 4 .26 4 .68 6.76 7.60 8.52 Deca ne 4.09 4.73 5.01 7 .53 8.50 9.56 T a b l e 3 He ats of a d s o r p t i c n (-AH) of a l c o hol s
on the c h e l a t e s st ud i e d S t a t i o n a r y phas e
Sou 1 te Ni (e n)A A Ni (t m ) AA N i (ph)AA N i ( e n ) B A Ni (t m)B A N i (p h )BA (-AH) (k ca l/nol) M e th ano l 3.61 3.72 3.75 3.74 3.70 3.69 F thanol 2.62 2.70 2 .62 2.33 2.65 3.26 Pr op ano l 3.50 3.90 3.95 4.37 4.81 5.53 Butanol 4 .40 5. 10 5.21 6.40 7.18 7.92 P e n t ano l 5.35 6.15 6.50 8.53 9.35 10.20 Hexanol 6.22 7.30 7 .80 10.60 11.65 12 . 48 iso-Pro-panol 1 .78 2.05 2.25 2.60 2.70 3.10 is o- Buta-nol 2.12 2.60 2.93 3.64 3.83 4.40 is o-Pen-tanol 2 .60 3.10 3.58 4 .60 5.10 5.7Ü se c - But a-nol 1.33 1.78 1.83 1.95 2.10 2.36 se c iso --P en tan ol 1.87 1.95 2.20 2.38 2.56 2.78 t e r t Bu -tanol 0.53 0.65 0.72 0.78 0.85 0.98
T a b l e 4 R e s u lts of re g r e s s i o n analysis for the f u n c t i o n (-a h) = f ( C N )
St a t i o n a r y phase Solu tes n- Alco hol s (C2 - C )x 6 n - A l k a n e s (C 5 ' p L1 0 ;)x a s b b R a s b b R N i ( e n ) A A 0.91 0.035 0 .78 0.9988 0.33 0.073 0.81 0.9987 N i (t m)A A 1.14 0.063 0.44 0.9995 0.45 0.065 0.25 0.9983 N i (ph)AA 1.29 0.075 0.08 0.9986 0.37 0 .087 1 . 39 0.9982 Ni (e n)B A 2 . OB 0.056 -1 .80 0.9981 0.75 0.043 0.05 0.9989 N i ( tm)BA 2.24 0.065 -1.83 0.9975 0.91 0.033 -0.55 0.9991 Ni (p h)8 A 2.32 0.087 -1 .38 0.9986 1.11 0.091 -1 .54 0.9993
N o t e : a = slope, s b = s t a n d a r d er ror of the slope, b = i n tercept, R = c o r r e l a t i o n co ef fic ie nt , x = numb er of c a rb on atoms in the solutes.
ch el ates, e.g. the a d s o r p t i o n on the N i (p h)A A is s t r o n g e r than those on N i ( t m ) A A or N i ( e n)A A complexes. For the c h e l a t e s wi th the same kind of h y d r o c a r b o n b r id ge it is seen that i n t r o d u c t i o n of p h e n y l e n e grou ps in the ch el a t e m o l e c u l e lead to an in crease in the heats of a d s o r p t i o n of the solu tes studied. Thus, it can be a s s u m e d that the c h e l a t e s s t u d ied d e a c t i v a t e s the su pp o r t su rf a c e in d i f f e r e n t way and that the i n c r eas ed s t a b i l i z a t i o n of these c h e l a t e s planar s t r u c t u r e may be in vo lve d in a d s o r p t i o n p h e n o m e n a [lO],
St r u c t u r a l ch an ges in the nick el (II) c h e l a t e s p r o d u c e a v a r i a tion in the GC c o l u mns s e l e c t i v i t y wh ich can be e x p r e s s e d by m e a s u ri ng d i f f e r e n c e s of the t h e r m o d y n a m i c q u a n t i t i e s invo lve d in the p r o c e s s e s of a d s o r p t i o n for some s e l e c t e d pairs of is omeric so lu tes
[ 11] . M e n t i o n e d values can be c a l c u l a t e d from equation:
& (A H ) _ A H 1 ~ A H 2 m
T - T <x)
w K er e A H j and A H ^ de no t e s the he ats of a d s o r p t i o n of the s o lu te 1 and ? r e sp ect iv el y, c o n s i d e r e d as c o n s t a n t in the n a r r o w t e m p e r a t u r e
range st udied, T the c o lu mn t e m p e ra tu re . This r e l a t i o n was e v a l u a t e d for the i s o m e t r i c pa irs of a l c o h o l s in the c o lu mn t e m p e r a t u r e equal 120 °C and is p r e s e n t e d in F i gu re 2 as the f u n c t i o n of m o l e c u l a r w e i g h t of the c h e l a t e s studied.
M.wt [ g/mol ]
Fig. 2. D i f f e r e n c e s in he ats of a d s o r p t i o n H/T and r e l a t i v e r e t e n tion upon s e p a r a t i o n at 120°C of the al co hol mixture: p r o p a n o l and i s o - p r o p a n o l c u rv es 1 and 3 or bu ta nol and is o - b u t a n o l c u rv es 2 and 4, as the f u nc tio n of m o l e c u l a r w e ig ht ch an g e s in the c h e l a t e s
stud ied
This figure shows that the s e p a r a t i o n of the line ar m o l e c u l e s with very slig ht d i f f e r e n c e in their e l e c t r o n d e n s i t y d i s t r i b u t i o n is p o s s i b l e by a p r o p e r l y m o d i f i e d s t r u c t u r e of s t a t i o n a r y phase. R e p l a c i n g a m e t h y l e n e g r ou ps wi th a phen yl s u b s t i t u e n t in the ch e l a t e s st ud i e d c o n s i d e r a b l y i n c r e a s e d the colu mn s e l e c t i v i t y . The ch a n ges in the r e l a t i v e r e t e n t i o n cx of alco hol pairs as the s t r u c t u r e of c h e l a t e s is vari ed (see F i gu re 2) are m e a n i n g f u l l in i l u s t r a t i n g some f e a t u r e s of the w o r k i n g ' m e c h a n i s m of such GC columns. For example
we assu me that s p e c ifi c a d s o r p t i o n of a l co hol s is s t r o ngl y influenced by ster ic effects. Thus, the e f f e c t i v e n e s s of the s e p a r a t i o n of the b r a n c h e d a l c o hol s m i x t u r e can be o p t i m i z e d by use N i ( p h ) B A ch el ate as the s t a t i o n a r y phase. An ot her i m p o rta nt factor a f f e c t i n g the a d s o r p t i o n p r o p e r t i e s of the nickel (II) c h el ate s s t u d i e d in volves the p o l y m e r i z a t i o n e q u i l l i b r i a in the solid stat e [12]. D i s t o r t i o n in the nickel (II) ch el a t e m o l e c u l e can i n f l uen ce h o m o m o l e c u l a r i n t e r a c t i o n and he nce their GC s e p a r a t i o n ability of d i f f e r e n t class of po lar compounds. These c o n s i d e r a t i o n s will be e x t e n d e d in the future c o mm uni ca ti ons .
A c k n o w l e d g e m e n t s
This work was s u p p o r t e d by a gr ant from the M i n i s t r y of Higher Ed uc ation, Poland, Pr oj ect MR 1 - 1 4 . I.7b.
J j l ^ e Q g e s
[1] C a r t o n i G . P . , L o w r i e R . S . , P h i l l i p s C. S . G . , V e n a n z i L. M., [in:] Gas C h r o m a t o g r a p h y , ed R.P. W. Scott, B u t t e r w o r t h s , London, 273 (I960).
[2] P f 1 a u m R. T., C o o k L. E., J. C h r o m at og r. , 50, 120 (1970). [3] G r ü n e s P., S a w 0 d n y W., J. Ch ro m a t o g r . , 3 2 2 , 63 (1985). [4] M a s ł o w s k a J . , B a z y l a k G., 3. Ch ro m a t o g r . , 2 9 8 , 211 (1984). [5] U d e n P. C., B 1 e s s e 1 K., Inorg. Chem., 12, 352(1973). [6] H 0 1 m R. H., J. Am. Chem. Soc., 82, 5632 (1960).
[7] M a s ł o w s k a J . , B a z y l a k G., Acta Chim. Hung, (s ub mit te d for publica ti on ).
[8] L a u b R. 3., P e c s o k R. L., P h y s i c o c h e m i c a l A p p l i c a tions of Gas C h r o m a t o g r a p h y , John Wi ley Sons, New York, 216 (1978).
[9] E t t r e L. S., C h r o m a t o g r a p h i a , ¿3, 73 (1980).
[10] J ä g e r E. G., Z. anorg. allg. chem., 3 6 4 , 177 (1969). [11] D i G o r c i a A . , L i b e r t i A . , S a m p e r i R., Anal.
C h e m . , 45, 1228 (1973).
Joanna Masłowska, Grzegorz Bazylak Joan na M a s ł ows ka , G r z e g o r z Ba zy l a k
W Y K O R Z Y S T A N I E K O M P L E K S Ó W Ni (II) Z ZA SA DAM I SC HI F F A JAKO FAZ S T A C J O N A R N Y C H W C H R O M A T O G R A F I I G A Z O W E J
B a d a n i a nad z a s t o s o w a n i e m r ó ż n y c h k o m p l e k s ó w meta li p r z e j ś c i o wych z dwu- i c z t e r o k l e s z c z o w y m i z a sa dam i S c h i f f a wy ka z a ł y , że zwią zki te s p e ł n i a j ą w y m a g a n i a s t a w i a n e fa zom s t a c j o n a r n y m s t o s o w a n y m w c h r o m a t o g r a f i i gazowej.
W p r z e d s t a w i o n e j p r ac y z b a d ano w p ły w m o d y f i k a c j i s t r u k t u r y li- gandu w s y m e t r y c z n y c h k o m p l e k s a c h Ni (II) na z d o l n o ś ć r o z d z i e l c z ą i w a r t o ś ć ciepeł ad so r p c j i a l k a n ó w i alkoholi. W tym celu nośnik d i a t o m i t o w y p o k r y w a n o w j e d n a k o w e j ilości (18%) k o l e j n o różn ymi s z e ś c i o m a c h e l ata mi Ni (II), u z y s k a n y m i na d r od ze k o n d e n s a c j i ace- ty l o a c e t o n u lub b e n z o i l o a c e t o n u i et yl eno -, p r o p y l e n o - lub fenyle- n o d i a m i n y .
St wi e r d z o n o , że w i e l k o ś ć o d d z i a ł y w a ń s p e c y f i c z n y c h m i e r z o n a z m i a nam i ciepeł a d s o rpc ji b a d a n y c h s o r b a t ó w u z a l e ż n i o n a jest od dł ug ośc i most ka a z o t - a z o t w c z ą s t e c z c e c z t e r o k l e s z c z o w e g o ch el a t u Ni (II). W p r o w a d z e n i e grupy f e n y l o w e j do c z ą s t e c z k i k o m p l e k s u p o w o du je w z ro st s e l e k t y w n o ś c i u z y s k a n y c h n o ś n i k ó w c h r o m a t o g r a f i c z ny ch na skutek w z r o stu en er gii o d d z i a ł y w a ń s p e c y f i c z n y c h k o m p l e k s m e t a l u - s o r b a t .
U m o ż l i w i ł o to o t r z y m a n i e s e l e k t y w n e g o r o z d z i a ł u par i z o m e r y c z nych alkoholi, p o r ó w n y w a l n e g o z r o z d z i a ł a m i u z y s k a n y m i w k l a s y c z nej c h r o m a t o g r a f i i gaz-ciecz.
Na s e l e k t y w n o ś ć u z y s k i w a n e g o r o z d z i a ł u a l ko hol i m o że mi eć t a k że w p ł y w różny s t o p i e ń p o l i m e r y z a c j i c z ą s t e c z e k b a d a n y c h k o m p l e k sów Ni (II) oraz t w o r z e n i e a d d u k t ó w m o l e k u l a r n y c h o różn ej t r w a ł o ści . U z y s k a n e wyni ki p o z w a l a j ą na p r z y p u s z c z e n i e , że w y p e ł n i e n i a z o p i s a n y m i k o m p l e k s a m i c h e l a t o w y m i Ni (II) o p ró cz z a s t o s o w a ń a n a l i t y c z n y c h mogą być w y k o r z y s t a n e do b a d a n i a o d d z i a ł y w a ń a d s o r b e n t - - a d s o r b a t .
