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Lanthanide(III) complexes of two oxaazadiamine macrocyclic ligands derived from 2,6-diformylpyridine: the crystal structures of a reduced macrocyclic ligand and the corresponding diprotonated macrocycle
ELSEVIER
Inorganica Chimica Acta 282 (1998) 42-49
Lanthanide(III) complexes of two oxaazadiamine macrocyclic ligands derived from 2,6-diformylpyridine: the crystal structures of a reduced macrocyclic ligand and the corresponding diprotonated macrocycle Laura Valencia ", Rufina Bastida "*, Andres de Bias b, David E. Fenton ~, Alejandro Mac~as a Adolfo Rodr~guez a, Teresa Rodriguez-Blas b Alfonso Castifieiras ~' •' Departamento de Qm'mica im~rgdnic~a. Unit'er.~idad de Sautiugo. Avenida de las Ciencias Jn. 157th5 Sunttu.~o de Compo.~'tefa. Spuin "Departamenu, tie Qm'mtca Ftmdamet~tal c bt&lxtrial. Universidad de Lu Coru~a. Campus th' la Zapateini s/n. 15071 l.u C,,rmiu, Spain • Department t!t'(?hemistry. The Univer.~io'. $3 7HFSheffieht. UK
Received 5 January 1998; receixed in revised fi~ml 3 March 1998: accepted 25 Starch 1998
Abstract
New macrocyclic lanthanide( ill ) complexes were obtained with two oxaazadiamine macrocycles derived from 2.6-diformylpyridine: ( i I mononuclear complexes of an I 8-membered sexidentate N ~O~ macrocycle ( L a) derived from 1.5-bis( 2-aminophenoxy )-3-oxapentane; ~ii ) mononuclear complexes of a 16-membered pentadentate N ,O: macrocycle (L-') derived from 1.3-bis(2-aminophenoxy) propane. The complexes were characterized by elemental analysis, molar conductivity, mass spectrometry. IR and ~H NMR spectroscopy, thermogravimetry and magnetic measurements. The crystal structures of the L-" macrocycle and the corresponding diprotonated ligand are also reported. © 1998 Elsevier Science S.A. All rights rese~.ed. IG,vword.~: Lanthanide complexes: Oxaazadiamine complexes: Crystal structt|re~.
1. I n t r o d u c t i o n
The stability of metal complexes with polydentate ligands depends on a range of factors such as the n u m b e r and type of donor atoms present and their relative positions within the ligand, the itature o f the ligand backbone, and the number and size of the chelate rings formed on complexation, if the ligand is a macrocycle, then the ring size ~s a further factor that will influence complex stability. Ccmsequently. macrocyclic iigand~ provide an excellent basis for the study o f molecular recognition p h e n o m e n a since their cavity size, shape, and c o m p o n e n t s can be varied readily [ 1 I. Within the area of macrocyclic chemistry, we are interested in the synthesis and characterization of ianthanide( !11 ) complexes with mixed N , O , donor-atom macrocycles containing aromatic, head and lateral units [ 2-51. Most efforts to date have focused on the use of Schiff-base macrocycles or tetraazapolyamine macrocycles as complexing agents for transi* Corresponding author. Fax: 34-81-597 525.
lion metal ions or for lanthanide( III ) ions. In contrast, little has been reported on lanthanide complexes with oxaazapolyamine macrocycles [ 6 - 1 0 ] . In previous papers we have reported the template synthesis of |anthanide( Ill ) complexes with related Schiff-base macrocycles containing pyridine [2,3,5] or furan [4l head units. As an extension of this work, we have investigated the reactions between hydrated lanthanide nitrates or perchlorates and the 18-membered oxaazadiamine macrocycle L', containing an N~O~-donor set, derived from 2,6-diformylpyridine and 1,5-bis( 2-aminophenoxy)-3-oxz 9entane, and the ! 6-membered oxaazadiamine macrocycle L-', containing an N,O_,-donor set, derived from 2,6-diformylpyridine and 1,3bis( 2-aminophenoxy ) propane. Ligands o f this type provide a series of c o m p o u n d s o f intermediate rigidity. The selective complexation and transport of metal ions may be facilitated by macrocyclic iigands of intermediate rigidity (that is, sufficient rigidity to present a donor set with a defined geometry to a metal ion. but flexible e n o u g h to encourage favourable kinetics of metal ion incorporation and release ).
0020-169319815 - ~ee front matter ,,~.~ 1998 Elsevier Science S.A, All rights reserved. PII S 0 0 2 0 - 1 6 9 3 ( 9 8 ~00186-8
L t k d e n c i u t't ul./Im,rgunica C h i m U , A c t a .I¢_ ~ ~ t!991¢/42--49
43
2.3. Preparations
t.vo..P
v
LI
~O
O"
v
L2
The object of this work aimed at evaluating how modifications introduced in these ligands led to increased ligand flexibility and how changes in the aliphatic bridge length could affect the coordination capacity towards lanthanide ions.
2. Exper, mental 2. !. Meusuremen£v Elemental analyses were carried out on a Fisons Instrument EA1108 C H N S - O elemental analyser. The IR spectra were recorded as KBr discs, using a Mattson C y g n u s 100 spectrophotometer. Fast atom b o m b a r d m e n t mass spectra were recorded on a Kratos M S 5 0 T C mass spectrometer. T h e matrix used was 3-nitrobenzyl alcohol. Melting points of the [ L n L I [ N O s l ~ c o m p l e x e s were determined using a Biichi capillary melting points apparatus. Magnetic measurements were determined at room temperature on a vibration sample m a g n e t o m e t e r ( V S M ) Digital M e a s u r e m e n t S y s t e m 1660 with a magnetic field of 5000 G. Conductivity measurements were carried out in 1 0 - ' mol d m ~ d i m e t h y l f o r m a m i d e or acetonitrile solutions at 20°C using a W T W LF3 conductimeter. T h e r m o g r a m s were obtained with a S h i m a d z u T G A - 5 0 thermogravimetric system under normal conditions, and with a Setaram T G A 92-16.18 (heating rate 5 K min ~; atmosphere He, 6t) c m ~ m i n ~ ) . 'H N M R spectra were recorded on a Bruker W M - 3 0 0 spectrometer.
2. 2. Chemicals and starting materials 2,6-Diformylpyridine was prepared according to the literature m e t h o d [ 11,121. T h e diamines 1,5-bis(2-aminopheno x y ) - 3 - o x a p e n t a n e and 1,3-bis(2-aminophenoxy) propane were prepared by reduction of the corresponding dinitro precursor using a procedure similar to that described previously [ 13,141. L a n t h a n i d e ( l l i ) nitrates and perchlorates were c o m m e r cial products from Alfa and Aldrich laboratories and were used without further purification. Solvents used were o f reagent grade and were purified by usual methods. Caution! Perchlorates are potentially explosive.
2.3.1. Synthesis of the diamine macroc3"cles L I and L'The metal-free reduced macrocycles were synthesized by a modification of previously reported procedures I 15 l- T h e y were prepared directly from an "in situ" reduction in methanol. with excess o f sodium tetrahydroborate, o f the corresponding metal diimine complexes, the lead( II ) perchlorate for L t. o r the manganese( ii ) perchlorate for L-'. T h e reaction solutions were refluxed for 1 h, then they were allowed to reach room temperature, and filtered. The products obtained were stirred with dichloromethane under reflux, filtered while hot, and the solutions concentrated to dryness to give the crude products, which were recrystallized from acetonitrile. L'. Yield 54%. Anal. Found: C, 65.6; H, 6.3; N, 9.8%. Calc. for C_,~H_,~N~O~- !,75H20: C. 65.3; H. 6.3: N, 9.9,%. Mass spectral parent peak ( F A B ) nd:: 392. IR ( K B r disc 9: ~'(HzO) 3537 c m ': v( NH ) 3410 and 3288 c m " ~. t H N M R ( D M S O - d , ) I see Table I ). Table I ' H N M R spectra o f L' and I L a L ' I [ C t O ~ I ,-6H.,O in DMSO-d~. L: and [ LaL-" I [ CIO~ I ~ 3 H . O in C D ,CN. and [ L-"H_, ] I CIO~ i., in DMSO-d~ Assignment
,5 ( p p m |
lnlegration
6 fppm)
IH 2H 4H 2H 8H 4H 4H
7.831t) 7.47(d) 4.39t s ~
1H 2H 4H
6.84--6.57t m) 4.101ml 3.851 m )
8H 4H 4H
|H 2H 4H 2H gH 4H 2H
8.4t(tl 7.84(d) 4.78(s)
IH 2H 4H
6.64--7.13t m) 4.40( t ~ 2.38 ( q )
8H 4H 2H
L: Ha Hb Hc Hd Aromatics He HI
7.711 t~ 7.39( d ~ 4.36c d ) 5.42( t ~ 6.85--6.50c m~ 4.11Ira) 3.851 m )
Ha Hb Hc Hd Aromatics He Hf
7.781t) 7.34( d ) 4.50( db 5.95( t ~ 6.65--.6.951m~ -1.281 t i 2.451 q j
Ha Hb Hc Hd Aromatics He Hf
8.221t) 7.80q d | 4.78( t ) 8.291 t ) 7.75-7.05(m) 4.421 t ) 2.471q )
Multiplicity
[ L a L : | [ C I O . i ~- 6H_,O
L-"
[ L a L : t [ C I O , I ,- 3 H : O
[ L:H., ] [ C I O , ] : IH 2H 4H 4H 8H 4H 2H
s: singlet, d: doublet, t: triplet, q; quintuplet, m: muhiplet. Hal
.]
~zJ
L,
!
44
L. Valencia et el./Inorganica Chimica Acta 282 (1998) 42--49
L -~.Yield 3 2 % . A n a l . Found: C, 73.5; H, 6.4; N, 11.8. Calc. for C,__,H,.~N,Oz: C, 73. ! ; H, 6.4; N, ! 1.6%. Mass spectral parent peak ( F A B ) nff:.: 362. IR ( K B r disc): u ( N H ) 3389 c m - t. IH N M R ( C D ~ C N ) (see Table 1). 2.3.2. G e n e r a l m e t h o d f o r the ~'nthesis o f lanthanide( lll) complexes A methanol solution { 10 c m ~) o f L n X 3 - n H 2 0 (0.50 m m o l ) ( X ffi NO.~ - or CIO4 - ) was added slowly to a w a r m stirred acetonitrile solution ( 5 0 c m ~) o f the ligand (0.50 m m o l ) . The re:.ultant solution was refluxed for about 4 h, filtered while hot and concentrated to -- ! 0 c m ~. T h e n diethyl ether was added to precipitate the complex. W h e n the c o m plex did not precipitate, it was necessary to evaporate the solvent and to add diethyl ether to the resulting oil. The product was filtered off, w a s h e d with methanol:diethyl ether ( I:! 0) and dried under vacuum. The c o m p l e x e s appear to be air stable, soluble in acetonitrile, dimethyl sulfoxide, dimet h y l f o r m a m i d e and acetone, m o d e r a t e l y soluble in methanol, ~thanol and dichloromethane, and insoluble in water, diethyl ether and carbon tetrachloride. All attempts to prepare c o m plexes o f L -~with l a n t h a n i d e ( I I I ) nitrates were unsuccessful. I L n L t l ( C I O 4 ) ~ - x H a O . IR {KBr disc): u ( C = C ) and u(C----N) 1450, 1600, 1 6 2 6 c m - ~ ; u(CIO.s- ) 626,636, 1087. I 118, 1143 c m - '; v(H_~O) 3400 c m - ~. Mass spectra (positive-ion F A B ) : observed peaks for J LnL' ( CIO.~ ) _,1 ' and [ L n L I ( CIO4 ) l + [LnLtI(NO~).~-xH_~O. IR ( K B r disc): v ( C = C ) and i , ( C = N ) 1450, 1600, 1 6 2 6 c m -~; ~,(NO~ ) 742, 815, 1035,
1325, 1384, 1500 cm - ~; v(H_,O) 3400 c m - ~. Mass spectra (positive-ion F A B ) : observed peaks for [LnL'(NO~)_~I + and [LnL~(NO~) 1 + [LnL21(CIO4).,.xH_~O. IR ( K B r disc): u ( C = C ) and v ( C = N ) 1450, 1602, 1 6 2 0 c m - i ; v ( C I O a - ) 626,636, 1087, 1120, ! 143 c m - ~; v(H_~O) 3400 c m - '. Mass spectra (positive-ion F A B ) : observed peaks for [LnL-'(CIO.~)_,] + and [ LnL:( CIO.; ) ] + 2.4. Cr3,stai structure data a n d determination
Crystal data and experimental conditions for L ~- and L-'H: [CIOa ]: are listed in Table 2. The molecular structures are illustrated in Figs. 1 and 2. Selected bond lengths and angles, with standard deviations in parentheses, are presented in Tables 3 and 4. A colourless prismati-: crystal o f C_,,H_, ~N ~O., and a yellow prismatic crystal o f [ C:aH2~N~O a ! I CIO~ ] _,were m o u n t e d on a glass fibre and used for data collection. Cell constants and an orientation matrix for data collection were obtained by least-squares refinement o f the diffraction data from 18 and 25 r e f e c t i o n s in the range 9 0 < 0 < 4 3 ° and 5 ° < 0 < 19 ° respectively in an Enraf-Nonius M A C H 3 automatic diffractometer [ 16]. Data w e r e collected at 293 K, using the to-2# scan technique for L-" and the to scan technique for L Z H , [ C 1 0 4 ] > and corrected for Lorentz and polarization effects [17]. An empirical absorption correction was also m a d e [ 18 ].
Table 2 Crystal data and structure refinement for L-"and L"Hd CIO~I_Empincal formula Formula weight Temperature (K) Wavelength (/~ ) Crystal system Space group Unit cell dimensions a (A 1 b (A) c CA) a (°1
C ::H,. ,N ,0: 361.43 293(2) 154184 orthorhombic Pnma
C :,H.,,CI :N ,0,,, 562.35 293(2) 0.71073 triclinic P- I
21.467(2) 15.0445(5) 5.8033(4)
8.476( 2 ) 10.824(9) 14.149110) 80.82(7)
(01 Y (°)
Volume ( ,/k'l Z Density (calc. ) ( Mg m ' ) Absorption coefficient (mm ' ) F(000) Crystal size (ram) 0 Range for data collection (°) lndexranges Reflections collected Independent reflections Data. parameters Goodness-of-fit on F: Final R indices (!> 2o'(1) ) Extinction coefficient Largest difference peak, hole ( e A ')
81.23(3) 81.30(3)
1874.2(2) 4 ! .281 0.666 768 0.40×0.10×0.10 4.12 to 64.94 -25
1255.8( 14 ) 2 1.487 0.320 584 0.35 ×0.15 ×0.15 3.70 to 22.82 - 9 < h < 0 , - I I < k _ < l l . -15_<1<15 3653 3381 ( R,n, = 0.1438) 3381, 305 0.965 R, = 0.0738, wR_,=0.1014 0.0008 (7)
0.373. - 0.362
45
L Valencia et a L / l n o r g a n i c a C h i m i c a A c t a 2 8 2 ¢ 1998.) 4 2 - 4 9
Table 3 Selected bond lengths ( A ) and angles (~) for L"
O-C(7)
N( 2 )==C(61 N121=-C(51 C( 2 )-=C( 3 ) C( 21-C( 51 C( 3 )-C141 C ( 6 ) - C ( I 1) C(6)--C(7) C( 7 l - C ( 8 ) C181-C191 C ( 9 ) - C ( 101 C( 10)-C( t I ) C( 121--C( 131
! .373(4) 1.428(5) 1.329(4) 1.37215 ) 1.462(51 1.388(6) 1.499(5 ) 1.373161 1.391(6) 1.410(5) 1.372461 1,381171 1.364( 71 1.387f61 1.500161
C ( 7 1 - O . . C ( 121 C( 21'-N( I )=-C( 2 ) C461-N121-C(51 N( I ) - C 1 2 1 - C ( 3 ) N( I )-.C( 21-C(51 C( 31-C( 21-C( 5 ) C(4)-C( 3 )-C(2) NI 2 )-C(51--C( 2 ) N( 2 ) - C ( 6 ) - C ( I I ) N( 2 )--C(6 )-C( 7 ) C( I I ) - C ( 6 ) - C ( 7 ) C( 8 ) - - C ( 7 ) - 0 C( 8)-(?( 7 )--C(6) O-C(71-C161 C( 7 )-.CI g)-C'( 9 ) C( I01--C(9)-C181 C191--C( tO)--C( 11 ) C( tO)--C( I I 1--C,61 O-=C( 121-=C( 131 C( 12 ) ' - C ( 1 3 ) - C ( 1 2 )
i I6.7141 118.215 ) 120.114) 123.0151 117.7(4) 119.3(51 ! 17.8161 110.6(4) 123.6(5) 119.2(4) 117.215) 125.8(51 120.715) 113.6141 120.616) 120.2(61 119.715) 121.7151 109.415) 118.9(7)
O-C(12) N( I )--C(2)
Tr A -~
_L,: I
W ct°
Fig_ I- Cry~tal smacturc of L: showing the atom labelling.
C4 '--~...~<~--J" "~'~'%r-~ ~.~
"©
~-
?
.,
\\
~
22
~
C23
22
Symmetry transformations used to generate equivalent atoms: ( i t x, - y + I / 2 . z. Table 4 Selected bond lengths ( A ) and angles (°) for L:H: [ CIO= ! ".
0=9
26
(b) Fig. 2. Two different views of L:H: [ CIO4 ] _. showing the atom labelling.
The structures were solved by direct methods [ 19 ] which revealed the position o f all non-hydrogen atoms, and refined on F-" by a full-matrix least-squares procedure using anisotropic displacement parameters for all non-hydrogen atoms [201. The hydrogen atoms were located on a difference
O( 151=-C(14) O( 15)--.C( 161 O( 19)--C(20)
1.37121 1.4211 ) 1.37(2)
O( 1 9 ) - C ( 1 8 ) N( I )--=C(61 N( i ) - C 1 2 ) N181--C(9) N( 8)--C(7) N( 261 =-C(25) N(26)-C(27) C(2')=.C(3) C( 2 )-=C(27) C(3)-C14) C( 41-=C151 C(5)--C(6)
!.42(2) 1.33121 1.36121 1.47(2) !.51( I ) 1.4612) 1.50{ I ) 1.37121 1.48( 21 1.38(2) 1.4212) 1.34(2) 1.51(21 1.3312) 1.39(2) 1.39(2) 1.40121
C(61--C(71 C(0)--.C(I0) C(9)-=C(14) C( 10)-C( 11 ) C( I I ) - C ( 121
(¢ontimtcd)
•.16
L. Vtde,r'ia et aL /lnrwganica Chimira Acta 282 (i 998J 42--49
Table 4 I continued )
[211. Molecular S C H A K A L [ 22].
C( 121-C( 131 C( 131~_'( 141 C( 161-C1171 C( 171--171181 C( 2111-C1251 C( 2(I)424 21 ) C(211-C(22) C( 22 )--('( 23 ) C(23 ]-C(24) C~ 24 ~-C( 25 I
1.40( 2 1.4(R 2 ) 1.47(2)
C1141-O( 15 I--C1161 C ( 2 0 ) - O l 19)-Cc lg) C{6~-N( I p--CI2) C( 9 ~-N( 8 I - C ( 7 ) C( 25 )-N( 261-C( 27 Nt I )-CI 2 I--C( 3 ) N( I )--Ct 2 ~--C(271 C13 ~--C(2)-Ct 27~ C~ 2 )-C( 3 )-C14 ~ C131--C141-C15~ C(6 ~-C~ 5 )--(_'(4 , Nt I ~-C(61--C151 N( I 1-('(61---C(7 ) C~ 5 ~-C.( 61-C( 7 ) NIg)-CI 7 ~--C(6I C( I O ) - C I q ) - C ( 14 ) C(101-C(9)-N(8) C(14)-C19l-N!8) C(9)--Ct I O ) - C ( I I ) CI IO)--C( I I ) - C ( 1 2 ) C( 131-C( 1 2 ) - C ( I i ) C( I4)-C( 13)-Ct 12) O( 15~-C(141--CI9)
118f I 11611 118(2 113( i
O( 15)-C1 14,-C1131 C(91--C1141-C( 13 ) Ol 15)--C( 16~-C( 171 C( 161-C( 171--C(IS)
O( 191-C( 18)-.C117~ C(25 ~-C.( 20 ~-0(It)) Ct 25 v-C(2() ~--Ct 21 O1191-C( 201-C~ 2t ) C[ 22)-C~ 21 ~-C( 20~ C121 ~-Ct 221-C(23) CI 22 )-C( 23 I-C(24) C(25 ~-C~ 241-C(23) C( 24 )-C( 25 I-C( 20 C124 i--C( 25 )-N~ 261 C~ 20 )--C( 25 )-N( 26 ) C( 2 )-C( 27 )-N(26)
1.51121
3. Results
1.3712 ) 1.38t 2 )
3. I. I_xmthanide( l l l ) complexe.~
1.36t21 1.36121 1.43121
1.34121
11541 t21t I !!511 12312 11912 11912 11712 12512 1t5(2 12112 1091 I
12412 12312 11412 120( 2
11912) 121(2) 11912b 1!9(2~ 124(21 118(21 109( 1) 1 t9(2)
|091 I ) 115(2) 1t8(2) 127q2) 12112b 122(29 119121
11712) t24121 i 19121
117~21 1(}7.3(8~
Fourier map and refined (so(topically ( w = I / Is"(F,, 2) + ( 0 . 0 5 1 3 P ) 2 + 0.0()00Pi w h e r e P = ( F,'- + 2F,-" ) / 3 ) for L:, and w e r e located in their calculated positions ( C - H 0 . 9 3 11.97 A,, N - H 0.90 A ) and refined using a riding model for L2H_, [ CIO.~] _,. A s e c o n d a r y extinction correction was only applied for L" [ 20 !- After all shift/e.s.d, natios were less than 0.001. the refinement c o n v e r g e d to the agreement factors listed in Table 2. For both structures, atomic scattering factors were taken from the International Tables for X-ray Crystallography
and
graphics
were
from
ZORTEP
and
discussion
In a previous paper, Fenton and c o w o r k e r s [ t5] reported the synthesis and characterization o f m o n o n u c l e a r C u ( l l ) nitrate c o m p l e x e s with the L ~and L-" macrocycles. W e investigated the a b o v e reaction using the less stereochemically d e m a n d i n g L n ( I I I ) cations in order to make a c o m p a r i s o n b e t w e e n the potential coordination b e h a v i o u r o f the reduced m a c r o c y c l i c ligands and their Schiff-base macrocyclic precursors and to analyse w h e t h e r the modification o f the n u m b e r o f d o n o r atoms, the change in the aliphatic bridge length, and the reduction o f the (mine groups could affect the synthesis and stability o f the c o m p l e x e s . W e have found that the reactions b e t w e e n L t and hydrated lanthanide nitrates or perchlorates in molar ratio 1:1. as described in Section 2, gave, in general, g o o d yields o f analytically pure products [ LnL' 1 [ C I O ~ ] , - x H 2 0 ( Ln = La, Ce, Pr, Nd, Eu, Gd, Tb, Ho or Er) and [Lnl,I1 [ NO~ 1~" xH_,O - vEt,O ( Ln = La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er or L u ) . The c o m p l e x e s I LnL-'I ! C I O , ] ~.xH_,O ( Ln = La, Ce, Pr, Sm, Eu, Gd, H o or Er) were obtained by reaction o f L 2 with hydrated lanthanide perchlorates but w e were unable to obtain c o m p l e x e s in the reactions attempted with L'- and the L n ( ! ! I ) nitrates where in all cases the free m a c r o c y c l e and unreacted metal salts separate out from the reaction m e d i u m on cooling to r o o m temperature. The c o m p l e x e s were characterized by elemental analysis (C. N, H ) , molar conductivity, magnetic m o m e n t measurements, thermal analyses ( nitrate c o m p l e x e s ) , mass spectrometry, IR s p e c t r o s c o p y , and ' H N M R s p e c t r o s c o p y for the diamagnetic lanthanum c o m p l e x e s . W e did not perform thermal analysis o f the perchlorate c o m p l e x e s because o f the e x p l o s i v e b e h a v i o u r s h o w n in earlier w o r k { 21. The analytical data and yields o f the reactions are presented in Table 5. C o m p a r i s o n o f these results with those obtained for the related diimine m a c r o c y c l e s containing pyridine [ 2,3 ! indicates that reduction o f the (mine groups increases the ligand flexibility, leading to an e n h a n c e m e n t o f the c o m p l e x at(on capacity o f both reduced systems, This effect is especially important at the end o f the lanthanide series, with the smaller lanthanide cations, w h e r e flexibility o f the ligand is necessary in order to allow the full set o f d o n o r atoms from the m a c r o c y c l e to approach the metal ions, The results also s h o w that the ligand derived from 1,5b i s ( 2 - a m i n o p h e n o x y ) - 3 - o x a p e n t a n e and containing a pyridine head unit provides a ligand f r a m e w o r k capable o f forming more stable l a n t h a n i d e ( I i i ) c o m p l e x e s than w h e n the furan head unit is used. In earlier w o r k we were unable to synthesize lanthanide c o m p l e x e s o f the furan-containing analogue o f L j 141.
L. Valencia et al. /lnvrgt~nica Chim& a Actu 282 ~199b~j 42-49 Table 5 Analytical data, yields and molar conductance data (in DMF ()r CH,CN) I LnL-'I ! CIO4 l~'xH-O x
47
for the comptexe~ I L n L ' I I C I O , 1 , - ~ H : O . [ L n L t I [ N O . I , . x H : O "and
Analysis ( % ) ' C
ILnL' I [ C I O , I , ..tH.,O 1_41 6 Ce 5 Pr 5 Nd 7 Eu 2 Gd 12 Th IO Fh) 12 Er 12
29.2 28.8 29.9 28.7 31.9 25.5 26.4 25.4 25.5
N 129.41 (28.81 (29.9) ! 28.7) { 31.41 ! 259) ( 26.8 ) t 25.8) ( 25.7 )
4.6 (4.5) 4.4 14.41 4.5 14.5 ) 4_5 (4.7) 4_4 (4.51 3.8 (3.6) 4+0 ( 4.4 ) 3.8 (3.7) 3.8 ( 3.8 )
Yield
.l~t
H
(C-)
( [ ! ~cm-'mol *)
4.11 (3.9) 3.2 13.61 "~.4 l 3.8 ) 3.4 (4.O) 3.2 ( 3.31 3.6 (4.6) 3.5 ( 4 3 ) 3.8 (4.5} 3.8 ( 4.5 )
53 79 88 711 68 65 76 59 68
419.9" 392.1 373.8 388.9 415.2 457.6 485.3 518,1 490.6
3.7 3.1 4.5 4.0 3.5 3.4 3.4 3.4 3.8 3.5 4.1
{3.81 ( 3.4 ) (5.1) (3.9) {4.2; 13.4) ( 3.41 (3.9) 1391 14.71 (4.11
66 60 17 16 81 5f) 78 61 54 13 42
133.14 't 152.9 169.5 183.7 170.4 172.0 ! 34.9 156.0 145.4 113.1 168.4
4.3 (3.4) 3.2 (2.~) 4.(1 ( 3.3 ) 3.8 (2.81 3.5 ( 3.5 ) 3.5 ( 3.9 ) 3.8 12.81 3.5 13.6t
70 31 62 54 59 82 63 73
380.5" 371.8 420.3 364.5 412.4 390.9 416.2 413.5
[ l-nL t 11 N O , l ,' xH,O
La Ce el. I, Nd h Eu Gd Tb Dy
5
Ho
3 3
Et )" Lu
5
36.6 136.71 30. I ( 38.5 ) 40_6 1411.21 30.2 139.51 33.3 {33.7) 36.9 ( 37.1 ) 36.7 ( 37.5 ) 34.6 (34.8) 34.7 134.6~ 41.5 (40.7) 3t.6132.71
[ LnL: l I CIO, l ," .d-I ~O La 3 Ce Pr 3 Sm Eu 4 Gd 7 Ht) 4 Er 5
31).g t 30.91 3 2 9 ( 33.111 3O2 t 3O3) ) 33.1 132.61 2g.2 {29.9 ) 27.7 ( 28.0 ) 32.5 ~32.111 28.7 '28+81
5 0.5
l i d ( I1.1 ) 12.3 ( I 1.7 ) 8-g t £).71 10.6 (II.O) I I.I ( 10.21 116 I I 1.31 I i.O { I 1.4 ) 10.6 ( IO.61 I 12 ( 10.51 t,)_8 ( 9 8 ) 11t.4 10.9) 5.2 5.5 5. l 5.5 4.9 4.5 5.5 4.6
(4.91 (5.2) ( 4.9 ) {521 ( 4.7 ) {4.4) 15.1 ) (4.6)
-' Calculated values in parentheses. h With y Et:O molecules: 1.5 t Pr): 0 5 ( Nd ): i.5 (Er). " !0 ~M in ace{on{{rile. '1 I0 ' M in dimethyl|'~lrmamide. 3.2. M a g n e t i c m e a s u r e m e n t s
measured
in d i m e t h y l f o r r n a m i d e ,
a r e in t h e r a n g e c h m a c t e r -
is{it o f 2: I e l e c t r o l y t e s in t h i s s o l v e n t , i n d i c a t i n g t h e w e a k e r T h e v a l u e s o f t h e m a g n e t i c m o m e n t s o f t h e [ L n L ' 1[ C I O 4 1 ~ c o m p l e x e s ( L n ~ C e , Dr, E u , G d , T b , H o a n d E r ; tz,.( B M ) = 2 . 7 0 , 2 . 9 8 , 2 . 9 0 , 7 . 2 4 , 9 . 0 2 , 9 . 9 7 , 8 . 0 3 ) s h o w little deviation from the theoretical values for tripositive lanthanide i o n s 1231 a n d t h o s e r e p o r t e d in t h e l i t e r a t u r e 1 2 4 , 2 5 1 , s u g g e s t i n g t h a t t h e 4 f e l e c t r o n s d o n o t p a r t i c i p a t e in b o n d f o r m a t { o n in t h e s e c o m p l e x e s . 3.3, M o k i r c o n d u c t i v i t i e s The molar conductance values for the perchlorate comp l e x e s o f L ' a n d L 2, m e a s u r e d in a c e t o n i t r i l e at 25°(2 ( T a b l e 5 ), lie in t h e r a n g e r e p o r t e d f o r 3: ! a n d 2:1 e l e c t r o l y t e s r e s p e c t i v e l y , T h i s s u g g e s t s t h a t in t h e l a t t e r c o m p l e x e s , d e r i v e d f r o m t h e s m a l l e r N a O , d o n o r set, a d d i t i o n a l c o o r d i n a t i o n o c c u r s via a perchlorate anion. For the nitrate complexes the values,
coordination capacity of the perchlorate anion [ 261-
3.4. T h e r m o g r a v i m e t r i c a n a l y s i s
Therrnogravimetric
analyses show that the [ LnL ) ] [ NO~ ] s
complexes produce similar thermograms, as a result of their similar structures. The TGA curves have stages up to 200°C w h i c h s h o w t h e y c o n t a i n s o l v e n t m o l e c u l e s , in a g r e e m e n t with the formulae proposed from the analytical data. Only w i t h L n = N d , E u , G d o r H o axe t h e r e c l e a r l y d e f i n e d m e l t i n g points. The other complexes
begin to decompose
in t h e t e m -
p e r a t u r e r a n g e 1 8 0 - - 2 4 0 ° C ; t h i s is l o w e r t h a n t h e t e m p e r a t u r e range observed for the related complexes of the diimine macrocycle (359-392°C) [ 21.
48
L. Valencia et aL / h~organica Chimica A,'ta 282 t 1998) 42--40
3.5. l A B m a s s spectra o f the complexes
The FAB mass spectral data confirm the formation of the [ LnL! X, complexes. In all cases, peaks assignable to metalcontaining fragments [LnL(CIO4)_,| ' , [LnL(CIO4) ] +, [ LnL( NO~)_, ! ~ and [ LnL( NO, ) 1 ' are present. Also, these fragments lose the metal ions to give the most intense peaks corresponding to the protonated ligand ( m / z = 392 for L' or 362 for L"). Peaks also appear for the nitrate complexes with L n = L a , Eu, Gd and Er, and for the Cel llI) perchlorate complex, which cc~rrespond to [LnL~I ' and [CeL~'l ' respectively. 3.6. IR spectra
The 1R spectra of the L' and L z ligands exhibit, in both cases, t,(N-H) vibrations in the 3320-3425 c m i region. The spectrum of the L ~ macrocycle shows a splitting of this vibration which most probably reflects different hydrogenbonding patterns for each of the secondary amine groups. In the IR spectra of the complexes, the secondary amine stretches are unassignable because there is an intense broad band centred at -,- 3400 cm J consistent with the presence of water as suggested from the microanalyticai data. The water present in the complexes can arise from either lattice a n d / o r coordinated water. The bands at about 1600 and 1450 cm ~ are associated with ~,( C = N ) and v ( C = C ) vibrations from the pyridine ring which undergo a shift towards high frequencies on complexation, suggesting interaction between the metal and the pyridine nitrogen atom [ 27 ]. The perchlorate assignments were made by comparison with literature values [28.29]. The splitting of the bands attributable to the asymmetric CI-O stretching mode at -.- ! 100 cm - ~ ( t,~ ) and the asymmetric CI-O bending mode (t,~) at ",- 620 cm ~ suggests coordination of at least one of the C104- anions, as is also suggested by the conductance measurements. The higher-energy band consists of three maxima at ~ 1140. 1120 and 1080 c m t: a similar splitting of the ~,~ band has been observed for lanthanide(lll) complexescontaining bidentate chelating CIO4 [30]. Although assignment of the nitrate vibrations in the IR spectra of the {LnLI ] [ NO x], complexes is more difficult, some information concerning the bonding mode of the nitrate ions can be obtained. In principle, ionic N O ~ has three IRactive vibrational modes at 1390, 830 and 720 c m - '; upon coordination of the anion the vibrations of higher and lower energies are split into two components and the fourth vibrational mode becomes IR allowed, so that six IR absorptions should be observed, v.~ and v~ at 710, 740 c m - 0 ~,~,at 820 c m J. ~ a t 1030cm ~, ~,.~and v~ at 1300, 1500cm-~ [311. The presence of several bands in the region associated with nitrate vibrations clearly identifies these species as containing coordinate nitrate groups [ 32]. In the spectra of all of the nitrate-containing complexes, the two most intense nitrate absorptions, associated with the v ( N = O ) and v~(NO_.),
appear at ~ 1500 and 1300 c m - t. The distinction between monodentate and bidentate nitrate groups is quite difficult, but the separation (A z,) of the two highest frequency bands has been used as a criterion to distinguish between the degree of covalence of the nitrate ,,,,ordination [33 ]. The magnitude of this separation of ~ 180 cm : may be indicative of a bidentate interaction of the nitrate anions with the lanthanide ions [34]. The appearance of an intense spectral band at ,-, 1380 cm I indicates the presence of some ionic nitrate group [ 35.36 ]. 3. Z N M R spectra o f the La(ilI) complexes
The ~H NMR spectrum of the diamagnetic [ LaL' ] [ CIO~ ], complex was recorded immediately after its dissolution in (CD~)_,SO and shows the expected signals (Table I ); the spectrum shows no meaningful change with time. On comparison with the spectrum of the free ligand, it can he seen that the signal assigned to the hydrogens of the amino groups does not appear, and that of the ¢t-CH: group to the amine is a singlet. The signals have almost the same position as in the free iigand, except for those of the pyridine hydrogen atoms which have been shifted downfield slightly. This behaviour contrasts with that observed for the corresponding Schiffbase ligand, which in the same solvent releases the metal ion slowly [2]. indicating that the increase in flexibility of the ligand leads to a more stable complex in the medium used. The 'H NMR spectra of the [LaL ~] [NO~ ], complex were recorded immediately after dissolution in (CD~),SO and CD~CN. The spectra were complex and show many signals, suggesting competition between the solvent and the ligand for the lanthanum. This could result in removal of the metal from the macrocycle, behaviour which we have observed already in other systems [ 2,3 l. The IH NMR spectrum for the [ LaL-" I [ C I O , ] , complex was recorded in C D , C N ( Table I ) and shows similar behavtour to that described for the corresponding perchlorate complex with the L ~ macrocycle. There was no change in the spectrum of the complex after ,-- 24 h. This result indicates a greater stability of the lanthanum perchlorate complexes in solution with both ligands. The complexes [LnL ~] [ClOt] ~-xH:O, Ln = C e , Eu and Tb, were examined by cyclic voltammetry at l 0 ~mol dm ~ in 10- ' tool d m - ~ EhNCIO~ in DMF: no oxidation-reduction processes were detected. 3.8. The cr3.'stal struct,,res o f L-" a n d L:H,ICI04I.,
Single crystals of the macrocycle L~" suitable for X-ray analysis were produced by recrystallization in acetonitrile. The crystal structure is shown in Fig. I. The molecular geometry is characterized by a crystallographic mirror plane running through C I 3 and dividing the pyridine ring. The macrocycle is bent with the benzene rings at an angle of 36.7(2) ° to each other. Crystals of composition [C2_-H_~.~N~O_,] [CIO412 were obtained by slow evaporation of an
L. Valencia et al. / hu~rganica Chimica At'ta 282 ¢ 1998,~ 4 2 - 4 9
acetonitrile solution of the [ LaL-" I [ CIO4 I," 3HzO complex. The diprotonated macrocycle is almost symmetrical, as shown in Fig. 2, although in this case there is no crystallographic mirror plane relating both halves of the molecule. The significant difference between the macrocycles lies in the environments of the N atoms of the amino groups. The C - N ( a m i n o ) distances increase on protonation ( C - N ! .371.46 A, and 1.46-1.51 ,~ for L-" and L-'H_, respectively). Also, and perhaps to 'accommodate' the perchlorate ions, the angles formed between the planes of the benzene tings and those of the pyridine ring increase notably ( from 2 i ° to 45°). The perchlorate anions are involved in hydrogen bonding interactions with the NH_, groups ( N ( 8 ) - O ( 1 ! ) 2.90( i ), N ( 8 ) - O ( 2 2 ) 2.93( I ), N ( 2 6 ) - O ( 1 3 ) 2.97(I). N ( 2 6 ) O( 13 ~) 2.91(I) ,$,). In both structures the remaining macrocyclic bond distances and bond angles are within the expected range of values.
4. S u p p l e m e n t a r y material
Further details of the crystal structure determination can be ordered from Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen. under the depository numbers CSD-408134 and CSD-408135 for L-" and L-'t.t, [ CIO+I_, respectively.
Acknowledgements We thank La Xunta de Galicia ( X U G A 20903B96) and {he University of La Corufia for financial support.
References I I1 (a) J.-M. Lehn. Science 227 (1985) 849; (b) J.-M. Lehn, Angew. Chem., Int. Ed. Engl. 27 { 1988) 89. 121 R. Bandin, R. Ba.stida, A. de Bias, P. Castro, D.E. Fenton. A. Mac/as, A. Rodtlguez, T. Rodr/guez-Blas, J. Chem. Soc., Dalton Trans. (1994) 1185. 131 R. Bastida, A. de Bias, P. Ca.~tro, D.E. Fenton, A. Macia.s, R. Rial. A. Rodn'guez, T. Rodr/guez-Blas. J. Chem. So¢.. Dalton Trans.( 19961 1493.
49
| 4 J H. Adamx. R. Ba_~tida. A. de Blab,. M. C a r n o ~ D . E lemon. A+M~ias, A. Rodn'guez. T. Rodn'guez-Blas, Polyhedron 16 {4p (1997) 567. [5l C. Lodeiro, R. Ba~tida, A. de Blas. D.E. lemon, A, Macias. A. Rodn'guez. T. Rodr/gucz-Blas. |norg. Chim. A c ~ 267 { 1998) 55. [6J DE. Fcntou. P.A. Vigato. Chem. Soc. Roy. 17 4"ISr88} 69. 17 ] P.V. Bernhardt.G.A. Lawrance. Coord. Chem. Rev. 104 (1990) 297. |81 P, Guerricro, S. Tamburini. P,A. Vigato, Co<~rd. Chem. Rev. 139 (1995) 17. [91 V. Alexander.Chem. Rev. 95 { 1995) 273. [ tO] MP. Hogerheide, J. Boersma, G. van Koten, Coord. C h c m Rev. I55 { 1996) 87. [ !1 ] EP. Papadoupoulus. A. Jarrar. C.H. Isstdoa'ides. J. Or E. Chem. 31 { 19(:~ ) 615. [ 121 D. J'erchel, J 1 Heider. H. Wagner. Liebigs Ann. Chem. 613 { 1958l 153. 1131 P-A- Taxker. EB. Fleischer, J. Am. Chem, So~. 92 c 1970) 7072. 1141 R.D. Cannon. B. Chiswell, L M . Venanzi. J. Chem. Soc. A t 1967) 1277. ! 151 D.E. Fenton. BP. Murphy. A.J. Leong [..F. Lindoy, A. Bashall, M. McPartlin, J. Chem. Sot:., Dalton Trans. (1987) 2543. [ 16l Enraf-Nonius. CAD4-Exptess Software, Version 5.1. Enraf-Nonius, Delft, 1995. [ 17l A.L- Spck. H E L E N A . a proffram for data reduction of C A D 4 data., University of Utrecht. Netherlands, 1993. [ 18} N. WMker. D. Stuart,Acta Crystallogr.,Sect. A 39 (1983) 15g 166. [ 19] G.M. Shcldrick. Acta C~stallo~r., Sect. A 4 6 { 1990) 467-473. {20] G+M. Sheldrick,SHELXL93, program for data refinement of cnjstal structures, University of G~lingen, Germany. 1993. 12 ! ] International Tables for X-ray Crystallography, Vol. C, Kluwer, Ootdrecht, Netherland,~. 1995. [ 22 i I a) L. Zsolnai, ZORTEP. a program for the presentation of thermal ellipsoids, University of Heidetberg. Germany, 1994: (b} E. Keller, SCHAKAL 92, J. Appl. Crystallogr. 22 (1989) 19. [23l L H Van Vleck, A. Frank, i~ys. Rev. 34 11929) 494; 34 (1929} 1625. [ 24] M. Mohan. I.P. Tandon, N.S. Gupta, J. lnorg. Nucl. Chem. 43 ( 1981 } 1224. 125 ] F.A. Hart, Comprehensive Coord. Chem. 3 (1987) 1059, Chap. 2. 126l W J . Geary, Coord+ Chem. Rev. 7 { 1971 ) 81. [ 271 N.S. Gill, R.H. Nunal|. D.E Scaife, J. [norg. Nucl. Chem. 18 { 1961 ) 79. [ 28l M.[:. Rosemhal. J. Chem. Educ. 50 (1973) 331. [ 29] A.J. Hathaway, A.E. Underhill+ J. Chem. Soc.( 1961 ) 3091. [ 301 L. De Cola, D . L Smiles. L M . Vallarino, Inorg. Chem. ~ ( 1986} 1729. 131 ] J.-C.G. Biinzli, D. Wessner, Coord. Chem. Rev. 191 (1984) 253. [ 32 ] W+T. Carnall, S. Siegel, J.R. Ferraro, B. Tani, E. GehetL Inorg. Chem. 12 (1973) 560. |33l JR. Fcrraro. J. lnorg. Nucl. Chem. 10 { 1959) 319. [_'14] P. Guerriero, U. Casellato. S. Tamburini, P.A. Vigato. R. Graziani, Inorg. Chim. Acta 129 ( 19~,7 j 127. { 351 N.F. Curtis, Y.M. Curtis, h,otg. Chem. 4 (1965) 804. [36] AB.P. Lever+ E. Mantovani, B.S. Ramaswamy. Can. J. Chem. 44 { 1971 ) 1957.
Inorganica Chimica Acta 282 (1998) 42-49
Lanthanide(III) complexes of two oxaazadiamine macrocyclic ligands derived from 2,6-diformylpyridine: the crystal structures of a reduced macrocyclic ligand and the corresponding diprotonated macrocycle Laura Valencia ", Rufina Bastida "*, Andres de Bias b, David E. Fenton ~, Alejandro Mac~as a Adolfo Rodr~guez a, Teresa Rodriguez-Blas b Alfonso Castifieiras ~' •' Departamento de Qm'mica im~rgdnic~a. Unit'er.~idad de Sautiugo. Avenida de las Ciencias Jn. 157th5 Sunttu.~o de Compo.~'tefa. Spuin "Departamenu, tie Qm'mtca Ftmdamet~tal c bt&lxtrial. Universidad de Lu Coru~a. Campus th' la Zapateini s/n. 15071 l.u C,,rmiu, Spain • Department t!t'(?hemistry. The Univer.~io'. $3 7HFSheffieht. UK
Received 5 January 1998; receixed in revised fi~ml 3 March 1998: accepted 25 Starch 1998
Abstract
New macrocyclic lanthanide( ill ) complexes were obtained with two oxaazadiamine macrocycles derived from 2.6-diformylpyridine: ( i I mononuclear complexes of an I 8-membered sexidentate N ~O~ macrocycle ( L a) derived from 1.5-bis( 2-aminophenoxy )-3-oxapentane; ~ii ) mononuclear complexes of a 16-membered pentadentate N ,O: macrocycle (L-') derived from 1.3-bis(2-aminophenoxy) propane. The complexes were characterized by elemental analysis, molar conductivity, mass spectrometry. IR and ~H NMR spectroscopy, thermogravimetry and magnetic measurements. The crystal structures of the L-" macrocycle and the corresponding diprotonated ligand are also reported. © 1998 Elsevier Science S.A. All rights rese~.ed. IG,vword.~: Lanthanide complexes: Oxaazadiamine complexes: Crystal structt|re~.
1. I n t r o d u c t i o n
The stability of metal complexes with polydentate ligands depends on a range of factors such as the n u m b e r and type of donor atoms present and their relative positions within the ligand, the itature o f the ligand backbone, and the number and size of the chelate rings formed on complexation, if the ligand is a macrocycle, then the ring size ~s a further factor that will influence complex stability. Ccmsequently. macrocyclic iigand~ provide an excellent basis for the study o f molecular recognition p h e n o m e n a since their cavity size, shape, and c o m p o n e n t s can be varied readily [ 1 I. Within the area of macrocyclic chemistry, we are interested in the synthesis and characterization of ianthanide( !11 ) complexes with mixed N , O , donor-atom macrocycles containing aromatic, head and lateral units [ 2-51. Most efforts to date have focused on the use of Schiff-base macrocycles or tetraazapolyamine macrocycles as complexing agents for transi* Corresponding author. Fax: 34-81-597 525.
lion metal ions or for lanthanide( III ) ions. In contrast, little has been reported on lanthanide complexes with oxaazapolyamine macrocycles [ 6 - 1 0 ] . In previous papers we have reported the template synthesis of |anthanide( Ill ) complexes with related Schiff-base macrocycles containing pyridine [2,3,5] or furan [4l head units. As an extension of this work, we have investigated the reactions between hydrated lanthanide nitrates or perchlorates and the 18-membered oxaazadiamine macrocycle L', containing an N~O~-donor set, derived from 2,6-diformylpyridine and 1,5-bis( 2-aminophenoxy)-3-oxz 9entane, and the ! 6-membered oxaazadiamine macrocycle L-', containing an N,O_,-donor set, derived from 2,6-diformylpyridine and 1,3bis( 2-aminophenoxy ) propane. Ligands o f this type provide a series of c o m p o u n d s o f intermediate rigidity. The selective complexation and transport of metal ions may be facilitated by macrocyclic iigands of intermediate rigidity (that is, sufficient rigidity to present a donor set with a defined geometry to a metal ion. but flexible e n o u g h to encourage favourable kinetics of metal ion incorporation and release ).
0020-169319815 - ~ee front matter ,,~.~ 1998 Elsevier Science S.A, All rights reserved. PII S 0 0 2 0 - 1 6 9 3 ( 9 8 ~00186-8
L t k d e n c i u t't ul./Im,rgunica C h i m U , A c t a .I¢_ ~ ~ t!991¢/42--49
43
2.3. Preparations
t.vo..P
v
LI
~O
O"
v
L2
The object of this work aimed at evaluating how modifications introduced in these ligands led to increased ligand flexibility and how changes in the aliphatic bridge length could affect the coordination capacity towards lanthanide ions.
2. Exper, mental 2. !. Meusuremen£v Elemental analyses were carried out on a Fisons Instrument EA1108 C H N S - O elemental analyser. The IR spectra were recorded as KBr discs, using a Mattson C y g n u s 100 spectrophotometer. Fast atom b o m b a r d m e n t mass spectra were recorded on a Kratos M S 5 0 T C mass spectrometer. T h e matrix used was 3-nitrobenzyl alcohol. Melting points of the [ L n L I [ N O s l ~ c o m p l e x e s were determined using a Biichi capillary melting points apparatus. Magnetic measurements were determined at room temperature on a vibration sample m a g n e t o m e t e r ( V S M ) Digital M e a s u r e m e n t S y s t e m 1660 with a magnetic field of 5000 G. Conductivity measurements were carried out in 1 0 - ' mol d m ~ d i m e t h y l f o r m a m i d e or acetonitrile solutions at 20°C using a W T W LF3 conductimeter. T h e r m o g r a m s were obtained with a S h i m a d z u T G A - 5 0 thermogravimetric system under normal conditions, and with a Setaram T G A 92-16.18 (heating rate 5 K min ~; atmosphere He, 6t) c m ~ m i n ~ ) . 'H N M R spectra were recorded on a Bruker W M - 3 0 0 spectrometer.
2. 2. Chemicals and starting materials 2,6-Diformylpyridine was prepared according to the literature m e t h o d [ 11,121. T h e diamines 1,5-bis(2-aminopheno x y ) - 3 - o x a p e n t a n e and 1,3-bis(2-aminophenoxy) propane were prepared by reduction of the corresponding dinitro precursor using a procedure similar to that described previously [ 13,141. L a n t h a n i d e ( l l i ) nitrates and perchlorates were c o m m e r cial products from Alfa and Aldrich laboratories and were used without further purification. Solvents used were o f reagent grade and were purified by usual methods. Caution! Perchlorates are potentially explosive.
2.3.1. Synthesis of the diamine macroc3"cles L I and L'The metal-free reduced macrocycles were synthesized by a modification of previously reported procedures I 15 l- T h e y were prepared directly from an "in situ" reduction in methanol. with excess o f sodium tetrahydroborate, o f the corresponding metal diimine complexes, the lead( II ) perchlorate for L t. o r the manganese( ii ) perchlorate for L-'. T h e reaction solutions were refluxed for 1 h, then they were allowed to reach room temperature, and filtered. The products obtained were stirred with dichloromethane under reflux, filtered while hot, and the solutions concentrated to dryness to give the crude products, which were recrystallized from acetonitrile. L'. Yield 54%. Anal. Found: C, 65.6; H, 6.3; N, 9.8%. Calc. for C_,~H_,~N~O~- !,75H20: C. 65.3; H. 6.3: N, 9.9,%. Mass spectral parent peak ( F A B ) nd:: 392. IR ( K B r disc 9: ~'(HzO) 3537 c m ': v( NH ) 3410 and 3288 c m " ~. t H N M R ( D M S O - d , ) I see Table I ). Table I ' H N M R spectra o f L' and I L a L ' I [ C t O ~ I ,-6H.,O in DMSO-d~. L: and [ LaL-" I [ CIO~ I ~ 3 H . O in C D ,CN. and [ L-"H_, ] I CIO~ i., in DMSO-d~ Assignment
,5 ( p p m |
lnlegration
6 fppm)
IH 2H 4H 2H 8H 4H 4H
7.831t) 7.47(d) 4.39t s ~
1H 2H 4H
6.84--6.57t m) 4.101ml 3.851 m )
8H 4H 4H
|H 2H 4H 2H gH 4H 2H
8.4t(tl 7.84(d) 4.78(s)
IH 2H 4H
6.64--7.13t m) 4.40( t ~ 2.38 ( q )
8H 4H 2H
L: Ha Hb Hc Hd Aromatics He HI
7.711 t~ 7.39( d ~ 4.36c d ) 5.42( t ~ 6.85--6.50c m~ 4.11Ira) 3.851 m )
Ha Hb Hc Hd Aromatics He Hf
7.781t) 7.34( d ) 4.50( db 5.95( t ~ 6.65--.6.951m~ -1.281 t i 2.451 q j
Ha Hb Hc Hd Aromatics He Hf
8.221t) 7.80q d | 4.78( t ) 8.291 t ) 7.75-7.05(m) 4.421 t ) 2.471q )
Multiplicity
[ L a L : | [ C I O . i ~- 6H_,O
L-"
[ L a L : t [ C I O , I ,- 3 H : O
[ L:H., ] [ C I O , ] : IH 2H 4H 4H 8H 4H 2H
s: singlet, d: doublet, t: triplet, q; quintuplet, m: muhiplet. Hal
.]
~zJ
L,
!
44
L. Valencia et el./Inorganica Chimica Acta 282 (1998) 42--49
L -~.Yield 3 2 % . A n a l . Found: C, 73.5; H, 6.4; N, 11.8. Calc. for C,__,H,.~N,Oz: C, 73. ! ; H, 6.4; N, ! 1.6%. Mass spectral parent peak ( F A B ) nff:.: 362. IR ( K B r disc): u ( N H ) 3389 c m - t. IH N M R ( C D ~ C N ) (see Table 1). 2.3.2. G e n e r a l m e t h o d f o r the ~'nthesis o f lanthanide( lll) complexes A methanol solution { 10 c m ~) o f L n X 3 - n H 2 0 (0.50 m m o l ) ( X ffi NO.~ - or CIO4 - ) was added slowly to a w a r m stirred acetonitrile solution ( 5 0 c m ~) o f the ligand (0.50 m m o l ) . The re:.ultant solution was refluxed for about 4 h, filtered while hot and concentrated to -- ! 0 c m ~. T h e n diethyl ether was added to precipitate the complex. W h e n the c o m plex did not precipitate, it was necessary to evaporate the solvent and to add diethyl ether to the resulting oil. The product was filtered off, w a s h e d with methanol:diethyl ether ( I:! 0) and dried under vacuum. The c o m p l e x e s appear to be air stable, soluble in acetonitrile, dimethyl sulfoxide, dimet h y l f o r m a m i d e and acetone, m o d e r a t e l y soluble in methanol, ~thanol and dichloromethane, and insoluble in water, diethyl ether and carbon tetrachloride. All attempts to prepare c o m plexes o f L -~with l a n t h a n i d e ( I I I ) nitrates were unsuccessful. I L n L t l ( C I O 4 ) ~ - x H a O . IR {KBr disc): u ( C = C ) and u(C----N) 1450, 1600, 1 6 2 6 c m - ~ ; u(CIO.s- ) 626,636, 1087. I 118, 1143 c m - '; v(H_~O) 3400 c m - ~. Mass spectra (positive-ion F A B ) : observed peaks for J LnL' ( CIO.~ ) _,1 ' and [ L n L I ( CIO4 ) l + [LnLtI(NO~).~-xH_~O. IR ( K B r disc): v ( C = C ) and i , ( C = N ) 1450, 1600, 1 6 2 6 c m -~; ~,(NO~ ) 742, 815, 1035,
1325, 1384, 1500 cm - ~; v(H_,O) 3400 c m - ~. Mass spectra (positive-ion F A B ) : observed peaks for [LnL'(NO~)_~I + and [LnL~(NO~) 1 + [LnL21(CIO4).,.xH_~O. IR ( K B r disc): u ( C = C ) and v ( C = N ) 1450, 1602, 1 6 2 0 c m - i ; v ( C I O a - ) 626,636, 1087, 1120, ! 143 c m - ~; v(H_~O) 3400 c m - '. Mass spectra (positive-ion F A B ) : observed peaks for [LnL-'(CIO.~)_,] + and [ LnL:( CIO.; ) ] + 2.4. Cr3,stai structure data a n d determination
Crystal data and experimental conditions for L ~- and L-'H: [CIOa ]: are listed in Table 2. The molecular structures are illustrated in Figs. 1 and 2. Selected bond lengths and angles, with standard deviations in parentheses, are presented in Tables 3 and 4. A colourless prismati-: crystal o f C_,,H_, ~N ~O., and a yellow prismatic crystal o f [ C:aH2~N~O a ! I CIO~ ] _,were m o u n t e d on a glass fibre and used for data collection. Cell constants and an orientation matrix for data collection were obtained by least-squares refinement o f the diffraction data from 18 and 25 r e f e c t i o n s in the range 9 0 < 0 < 4 3 ° and 5 ° < 0 < 19 ° respectively in an Enraf-Nonius M A C H 3 automatic diffractometer [ 16]. Data w e r e collected at 293 K, using the to-2# scan technique for L-" and the to scan technique for L Z H , [ C 1 0 4 ] > and corrected for Lorentz and polarization effects [17]. An empirical absorption correction was also m a d e [ 18 ].
Table 2 Crystal data and structure refinement for L-"and L"Hd CIO~I_Empincal formula Formula weight Temperature (K) Wavelength (/~ ) Crystal system Space group Unit cell dimensions a (A 1 b (A) c CA) a (°1
C ::H,. ,N ,0: 361.43 293(2) 154184 orthorhombic Pnma
C :,H.,,CI :N ,0,,, 562.35 293(2) 0.71073 triclinic P- I
21.467(2) 15.0445(5) 5.8033(4)
8.476( 2 ) 10.824(9) 14.149110) 80.82(7)
(01 Y (°)
Volume ( ,/k'l Z Density (calc. ) ( Mg m ' ) Absorption coefficient (mm ' ) F(000) Crystal size (ram) 0 Range for data collection (°) lndexranges Reflections collected Independent reflections Data. parameters Goodness-of-fit on F: Final R indices (!> 2o'(1) ) Extinction coefficient Largest difference peak, hole ( e A ')
81.23(3) 81.30(3)
1874.2(2) 4 ! .281 0.666 768 0.40×0.10×0.10 4.12 to 64.94 -25
1255.8( 14 ) 2 1.487 0.320 584 0.35 ×0.15 ×0.15 3.70 to 22.82 - 9 < h < 0 , - I I < k _ < l l . -15_<1<15 3653 3381 ( R,n, = 0.1438) 3381, 305 0.965 R, = 0.0738, wR_,=0.1014 0.0008 (7)
0.373. - 0.362
45
L Valencia et a L / l n o r g a n i c a C h i m i c a A c t a 2 8 2 ¢ 1998.) 4 2 - 4 9
Table 3 Selected bond lengths ( A ) and angles (~) for L"
O-C(7)
N( 2 )==C(61 N121=-C(51 C( 2 )-=C( 3 ) C( 21-C( 51 C( 3 )-C141 C ( 6 ) - C ( I 1) C(6)--C(7) C( 7 l - C ( 8 ) C181-C191 C ( 9 ) - C ( 101 C( 10)-C( t I ) C( 121--C( 131
! .373(4) 1.428(5) 1.329(4) 1.37215 ) 1.462(51 1.388(6) 1.499(5 ) 1.373161 1.391(6) 1.410(5) 1.372461 1,381171 1.364( 71 1.387f61 1.500161
C ( 7 1 - O . . C ( 121 C( 21'-N( I )=-C( 2 ) C461-N121-C(51 N( I ) - C 1 2 1 - C ( 3 ) N( I )-.C( 21-C(51 C( 31-C( 21-C( 5 ) C(4)-C( 3 )-C(2) NI 2 )-C(51--C( 2 ) N( 2 ) - C ( 6 ) - C ( I I ) N( 2 )--C(6 )-C( 7 ) C( I I ) - C ( 6 ) - C ( 7 ) C( 8 ) - - C ( 7 ) - 0 C( 8)-(?( 7 )--C(6) O-C(71-C161 C( 7 )-.CI g)-C'( 9 ) C( I01--C(9)-C181 C191--C( tO)--C( 11 ) C( tO)--C( I I 1--C,61 O-=C( 121-=C( 131 C( 12 ) ' - C ( 1 3 ) - C ( 1 2 )
i I6.7141 118.215 ) 120.114) 123.0151 117.7(4) 119.3(51 ! 17.8161 110.6(4) 123.6(5) 119.2(4) 117.215) 125.8(51 120.715) 113.6141 120.616) 120.2(61 119.715) 121.7151 109.415) 118.9(7)
O-C(12) N( I )--C(2)
Tr A -~
_L,: I
W ct°
Fig_ I- Cry~tal smacturc of L: showing the atom labelling.
C4 '--~...~<~--J" "~'~'%r-~ ~.~
"©
~-
?
.,
\\
~
22
~
C23
22
Symmetry transformations used to generate equivalent atoms: ( i t x, - y + I / 2 . z. Table 4 Selected bond lengths ( A ) and angles (°) for L:H: [ CIO= ! ".
0=9
26
(b) Fig. 2. Two different views of L:H: [ CIO4 ] _. showing the atom labelling.
The structures were solved by direct methods [ 19 ] which revealed the position o f all non-hydrogen atoms, and refined on F-" by a full-matrix least-squares procedure using anisotropic displacement parameters for all non-hydrogen atoms [201. The hydrogen atoms were located on a difference
O( 151=-C(14) O( 15)--.C( 161 O( 19)--C(20)
1.37121 1.4211 ) 1.37(2)
O( 1 9 ) - C ( 1 8 ) N( I )--=C(61 N( i ) - C 1 2 ) N181--C(9) N( 8)--C(7) N( 261 =-C(25) N(26)-C(27) C(2')=.C(3) C( 2 )-=C(27) C(3)-C14) C( 41-=C151 C(5)--C(6)
!.42(2) 1.33121 1.36121 1.47(2) !.51( I ) 1.4612) 1.50{ I ) 1.37121 1.48( 21 1.38(2) 1.4212) 1.34(2) 1.51(21 1.3312) 1.39(2) 1.39(2) 1.40121
C(61--C(71 C(0)--.C(I0) C(9)-=C(14) C( 10)-C( 11 ) C( I I ) - C ( 121
(¢ontimtcd)
•.16
L. Vtde,r'ia et aL /lnrwganica Chimira Acta 282 (i 998J 42--49
Table 4 I continued )
[211. Molecular S C H A K A L [ 22].
C( 121-C( 131 C( 131~_'( 141 C( 161-C1171 C( 171--171181 C( 2111-C1251 C( 2(I)424 21 ) C(211-C(22) C( 22 )--('( 23 ) C(23 ]-C(24) C~ 24 ~-C( 25 I
1.40( 2 1.4(R 2 ) 1.47(2)
C1141-O( 15 I--C1161 C ( 2 0 ) - O l 19)-Cc lg) C{6~-N( I p--CI2) C( 9 ~-N( 8 I - C ( 7 ) C( 25 )-N( 261-C( 27 Nt I )-CI 2 I--C( 3 ) N( I )--Ct 2 ~--C(271 C13 ~--C(2)-Ct 27~ C~ 2 )-C( 3 )-C14 ~ C131--C141-C15~ C(6 ~-C~ 5 )--(_'(4 , Nt I ~-C(61--C151 N( I 1-('(61---C(7 ) C~ 5 ~-C.( 61-C( 7 ) NIg)-CI 7 ~--C(6I C( I O ) - C I q ) - C ( 14 ) C(101-C(9)-N(8) C(14)-C19l-N!8) C(9)--Ct I O ) - C ( I I ) CI IO)--C( I I ) - C ( 1 2 ) C( 131-C( 1 2 ) - C ( I i ) C( I4)-C( 13)-Ct 12) O( 15~-C(141--CI9)
118f I 11611 118(2 113( i
O( 15)-C1 14,-C1131 C(91--C1141-C( 13 ) Ol 15)--C( 16~-C( 171 C( 161-C( 171--C(IS)
O( 191-C( 18)-.C117~ C(25 ~-C.( 20 ~-0(It)) Ct 25 v-C(2() ~--Ct 21 O1191-C( 201-C~ 2t ) C[ 22)-C~ 21 ~-C( 20~ C121 ~-Ct 221-C(23) CI 22 )-C( 23 I-C(24) C(25 ~-C~ 241-C(23) C( 24 )-C( 25 I-C( 20 C124 i--C( 25 )-N~ 261 C~ 20 )--C( 25 )-N( 26 ) C( 2 )-C( 27 )-N(26)
1.51121
3. Results
1.3712 ) 1.38t 2 )
3. I. I_xmthanide( l l l ) complexe.~
1.36t21 1.36121 1.43121
1.34121
11541 t21t I !!511 12312 11912 11912 11712 12512 1t5(2 12112 1091 I
12412 12312 11412 120( 2
11912) 121(2) 11912b 1!9(2~ 124(21 118(21 109( 1) 1 t9(2)
|091 I ) 115(2) 1t8(2) 127q2) 12112b 122(29 119121
11712) t24121 i 19121
117~21 1(}7.3(8~
Fourier map and refined (so(topically ( w = I / Is"(F,, 2) + ( 0 . 0 5 1 3 P ) 2 + 0.0()00Pi w h e r e P = ( F,'- + 2F,-" ) / 3 ) for L:, and w e r e located in their calculated positions ( C - H 0 . 9 3 11.97 A,, N - H 0.90 A ) and refined using a riding model for L2H_, [ CIO.~] _,. A s e c o n d a r y extinction correction was only applied for L" [ 20 !- After all shift/e.s.d, natios were less than 0.001. the refinement c o n v e r g e d to the agreement factors listed in Table 2. For both structures, atomic scattering factors were taken from the International Tables for X-ray Crystallography
and
graphics
were
from
ZORTEP
and
discussion
In a previous paper, Fenton and c o w o r k e r s [ t5] reported the synthesis and characterization o f m o n o n u c l e a r C u ( l l ) nitrate c o m p l e x e s with the L ~and L-" macrocycles. W e investigated the a b o v e reaction using the less stereochemically d e m a n d i n g L n ( I I I ) cations in order to make a c o m p a r i s o n b e t w e e n the potential coordination b e h a v i o u r o f the reduced m a c r o c y c l i c ligands and their Schiff-base macrocyclic precursors and to analyse w h e t h e r the modification o f the n u m b e r o f d o n o r atoms, the change in the aliphatic bridge length, and the reduction o f the (mine groups could affect the synthesis and stability o f the c o m p l e x e s . W e have found that the reactions b e t w e e n L t and hydrated lanthanide nitrates or perchlorates in molar ratio 1:1. as described in Section 2, gave, in general, g o o d yields o f analytically pure products [ LnL' 1 [ C I O ~ ] , - x H 2 0 ( Ln = La, Ce, Pr, Nd, Eu, Gd, Tb, Ho or Er) and [Lnl,I1 [ NO~ 1~" xH_,O - vEt,O ( Ln = La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er or L u ) . The c o m p l e x e s I LnL-'I ! C I O , ] ~.xH_,O ( Ln = La, Ce, Pr, Sm, Eu, Gd, H o or Er) were obtained by reaction o f L 2 with hydrated lanthanide perchlorates but w e were unable to obtain c o m p l e x e s in the reactions attempted with L'- and the L n ( ! ! I ) nitrates where in all cases the free m a c r o c y c l e and unreacted metal salts separate out from the reaction m e d i u m on cooling to r o o m temperature. The c o m p l e x e s were characterized by elemental analysis (C. N, H ) , molar conductivity, magnetic m o m e n t measurements, thermal analyses ( nitrate c o m p l e x e s ) , mass spectrometry, IR s p e c t r o s c o p y , and ' H N M R s p e c t r o s c o p y for the diamagnetic lanthanum c o m p l e x e s . W e did not perform thermal analysis o f the perchlorate c o m p l e x e s because o f the e x p l o s i v e b e h a v i o u r s h o w n in earlier w o r k { 21. The analytical data and yields o f the reactions are presented in Table 5. C o m p a r i s o n o f these results with those obtained for the related diimine m a c r o c y c l e s containing pyridine [ 2,3 ! indicates that reduction o f the (mine groups increases the ligand flexibility, leading to an e n h a n c e m e n t o f the c o m p l e x at(on capacity o f both reduced systems, This effect is especially important at the end o f the lanthanide series, with the smaller lanthanide cations, w h e r e flexibility o f the ligand is necessary in order to allow the full set o f d o n o r atoms from the m a c r o c y c l e to approach the metal ions, The results also s h o w that the ligand derived from 1,5b i s ( 2 - a m i n o p h e n o x y ) - 3 - o x a p e n t a n e and containing a pyridine head unit provides a ligand f r a m e w o r k capable o f forming more stable l a n t h a n i d e ( I i i ) c o m p l e x e s than w h e n the furan head unit is used. In earlier w o r k we were unable to synthesize lanthanide c o m p l e x e s o f the furan-containing analogue o f L j 141.
L. Valencia et al. /lnvrgt~nica Chim& a Actu 282 ~199b~j 42-49 Table 5 Analytical data, yields and molar conductance data (in DMF ()r CH,CN) I LnL-'I ! CIO4 l~'xH-O x
47
for the comptexe~ I L n L ' I I C I O , 1 , - ~ H : O . [ L n L t I [ N O . I , . x H : O "and
Analysis ( % ) ' C
ILnL' I [ C I O , I , ..tH.,O 1_41 6 Ce 5 Pr 5 Nd 7 Eu 2 Gd 12 Th IO Fh) 12 Er 12
29.2 28.8 29.9 28.7 31.9 25.5 26.4 25.4 25.5
N 129.41 (28.81 (29.9) ! 28.7) { 31.41 ! 259) ( 26.8 ) t 25.8) ( 25.7 )
4.6 (4.5) 4.4 14.41 4.5 14.5 ) 4_5 (4.7) 4_4 (4.51 3.8 (3.6) 4+0 ( 4.4 ) 3.8 (3.7) 3.8 ( 3.8 )
Yield
.l~t
H
(C-)
( [ ! ~cm-'mol *)
4.11 (3.9) 3.2 13.61 "~.4 l 3.8 ) 3.4 (4.O) 3.2 ( 3.31 3.6 (4.6) 3.5 ( 4 3 ) 3.8 (4.5} 3.8 ( 4.5 )
53 79 88 711 68 65 76 59 68
419.9" 392.1 373.8 388.9 415.2 457.6 485.3 518,1 490.6
3.7 3.1 4.5 4.0 3.5 3.4 3.4 3.4 3.8 3.5 4.1
{3.81 ( 3.4 ) (5.1) (3.9) {4.2; 13.4) ( 3.41 (3.9) 1391 14.71 (4.11
66 60 17 16 81 5f) 78 61 54 13 42
133.14 't 152.9 169.5 183.7 170.4 172.0 ! 34.9 156.0 145.4 113.1 168.4
4.3 (3.4) 3.2 (2.~) 4.(1 ( 3.3 ) 3.8 (2.81 3.5 ( 3.5 ) 3.5 ( 3.9 ) 3.8 12.81 3.5 13.6t
70 31 62 54 59 82 63 73
380.5" 371.8 420.3 364.5 412.4 390.9 416.2 413.5
[ l-nL t 11 N O , l ,' xH,O
La Ce el. I, Nd h Eu Gd Tb Dy
5
Ho
3 3
Et )" Lu
5
36.6 136.71 30. I ( 38.5 ) 40_6 1411.21 30.2 139.51 33.3 {33.7) 36.9 ( 37.1 ) 36.7 ( 37.5 ) 34.6 (34.8) 34.7 134.6~ 41.5 (40.7) 3t.6132.71
[ LnL: l I CIO, l ," .d-I ~O La 3 Ce Pr 3 Sm Eu 4 Gd 7 Ht) 4 Er 5
31).g t 30.91 3 2 9 ( 33.111 3O2 t 3O3) ) 33.1 132.61 2g.2 {29.9 ) 27.7 ( 28.0 ) 32.5 ~32.111 28.7 '28+81
5 0.5
l i d ( I1.1 ) 12.3 ( I 1.7 ) 8-g t £).71 10.6 (II.O) I I.I ( 10.21 116 I I 1.31 I i.O { I 1.4 ) 10.6 ( IO.61 I 12 ( 10.51 t,)_8 ( 9 8 ) 11t.4 10.9) 5.2 5.5 5. l 5.5 4.9 4.5 5.5 4.6
(4.91 (5.2) ( 4.9 ) {521 ( 4.7 ) {4.4) 15.1 ) (4.6)
-' Calculated values in parentheses. h With y Et:O molecules: 1.5 t Pr): 0 5 ( Nd ): i.5 (Er). " !0 ~M in ace{on{{rile. '1 I0 ' M in dimethyl|'~lrmamide. 3.2. M a g n e t i c m e a s u r e m e n t s
measured
in d i m e t h y l f o r r n a m i d e ,
a r e in t h e r a n g e c h m a c t e r -
is{it o f 2: I e l e c t r o l y t e s in t h i s s o l v e n t , i n d i c a t i n g t h e w e a k e r T h e v a l u e s o f t h e m a g n e t i c m o m e n t s o f t h e [ L n L ' 1[ C I O 4 1 ~ c o m p l e x e s ( L n ~ C e , Dr, E u , G d , T b , H o a n d E r ; tz,.( B M ) = 2 . 7 0 , 2 . 9 8 , 2 . 9 0 , 7 . 2 4 , 9 . 0 2 , 9 . 9 7 , 8 . 0 3 ) s h o w little deviation from the theoretical values for tripositive lanthanide i o n s 1231 a n d t h o s e r e p o r t e d in t h e l i t e r a t u r e 1 2 4 , 2 5 1 , s u g g e s t i n g t h a t t h e 4 f e l e c t r o n s d o n o t p a r t i c i p a t e in b o n d f o r m a t { o n in t h e s e c o m p l e x e s . 3.3, M o k i r c o n d u c t i v i t i e s The molar conductance values for the perchlorate comp l e x e s o f L ' a n d L 2, m e a s u r e d in a c e t o n i t r i l e at 25°(2 ( T a b l e 5 ), lie in t h e r a n g e r e p o r t e d f o r 3: ! a n d 2:1 e l e c t r o l y t e s r e s p e c t i v e l y , T h i s s u g g e s t s t h a t in t h e l a t t e r c o m p l e x e s , d e r i v e d f r o m t h e s m a l l e r N a O , d o n o r set, a d d i t i o n a l c o o r d i n a t i o n o c c u r s via a perchlorate anion. For the nitrate complexes the values,
coordination capacity of the perchlorate anion [ 261-
3.4. T h e r m o g r a v i m e t r i c a n a l y s i s
Therrnogravimetric
analyses show that the [ LnL ) ] [ NO~ ] s
complexes produce similar thermograms, as a result of their similar structures. The TGA curves have stages up to 200°C w h i c h s h o w t h e y c o n t a i n s o l v e n t m o l e c u l e s , in a g r e e m e n t with the formulae proposed from the analytical data. Only w i t h L n = N d , E u , G d o r H o axe t h e r e c l e a r l y d e f i n e d m e l t i n g points. The other complexes
begin to decompose
in t h e t e m -
p e r a t u r e r a n g e 1 8 0 - - 2 4 0 ° C ; t h i s is l o w e r t h a n t h e t e m p e r a t u r e range observed for the related complexes of the diimine macrocycle (359-392°C) [ 21.
48
L. Valencia et aL / h~organica Chimica A,'ta 282 t 1998) 42--40
3.5. l A B m a s s spectra o f the complexes
The FAB mass spectral data confirm the formation of the [ LnL! X, complexes. In all cases, peaks assignable to metalcontaining fragments [LnL(CIO4)_,| ' , [LnL(CIO4) ] +, [ LnL( NO~)_, ! ~ and [ LnL( NO, ) 1 ' are present. Also, these fragments lose the metal ions to give the most intense peaks corresponding to the protonated ligand ( m / z = 392 for L' or 362 for L"). Peaks also appear for the nitrate complexes with L n = L a , Eu, Gd and Er, and for the Cel llI) perchlorate complex, which cc~rrespond to [LnL~I ' and [CeL~'l ' respectively. 3.6. IR spectra
The 1R spectra of the L' and L z ligands exhibit, in both cases, t,(N-H) vibrations in the 3320-3425 c m i region. The spectrum of the L ~ macrocycle shows a splitting of this vibration which most probably reflects different hydrogenbonding patterns for each of the secondary amine groups. In the IR spectra of the complexes, the secondary amine stretches are unassignable because there is an intense broad band centred at -,- 3400 cm J consistent with the presence of water as suggested from the microanalyticai data. The water present in the complexes can arise from either lattice a n d / o r coordinated water. The bands at about 1600 and 1450 cm ~ are associated with ~,( C = N ) and v ( C = C ) vibrations from the pyridine ring which undergo a shift towards high frequencies on complexation, suggesting interaction between the metal and the pyridine nitrogen atom [ 27 ]. The perchlorate assignments were made by comparison with literature values [28.29]. The splitting of the bands attributable to the asymmetric CI-O stretching mode at -.- ! 100 cm - ~ ( t,~ ) and the asymmetric CI-O bending mode (t,~) at ",- 620 cm ~ suggests coordination of at least one of the C104- anions, as is also suggested by the conductance measurements. The higher-energy band consists of three maxima at ~ 1140. 1120 and 1080 c m t: a similar splitting of the ~,~ band has been observed for lanthanide(lll) complexescontaining bidentate chelating CIO4 [30]. Although assignment of the nitrate vibrations in the IR spectra of the {LnLI ] [ NO x], complexes is more difficult, some information concerning the bonding mode of the nitrate ions can be obtained. In principle, ionic N O ~ has three IRactive vibrational modes at 1390, 830 and 720 c m - '; upon coordination of the anion the vibrations of higher and lower energies are split into two components and the fourth vibrational mode becomes IR allowed, so that six IR absorptions should be observed, v.~ and v~ at 710, 740 c m - 0 ~,~,at 820 c m J. ~ a t 1030cm ~, ~,.~and v~ at 1300, 1500cm-~ [311. The presence of several bands in the region associated with nitrate vibrations clearly identifies these species as containing coordinate nitrate groups [ 32]. In the spectra of all of the nitrate-containing complexes, the two most intense nitrate absorptions, associated with the v ( N = O ) and v~(NO_.),
appear at ~ 1500 and 1300 c m - t. The distinction between monodentate and bidentate nitrate groups is quite difficult, but the separation (A z,) of the two highest frequency bands has been used as a criterion to distinguish between the degree of covalence of the nitrate ,,,,ordination [33 ]. The magnitude of this separation of ~ 180 cm : may be indicative of a bidentate interaction of the nitrate anions with the lanthanide ions [34]. The appearance of an intense spectral band at ,-, 1380 cm I indicates the presence of some ionic nitrate group [ 35.36 ]. 3. Z N M R spectra o f the La(ilI) complexes
The ~H NMR spectrum of the diamagnetic [ LaL' ] [ CIO~ ], complex was recorded immediately after its dissolution in (CD~)_,SO and shows the expected signals (Table I ); the spectrum shows no meaningful change with time. On comparison with the spectrum of the free ligand, it can he seen that the signal assigned to the hydrogens of the amino groups does not appear, and that of the ¢t-CH: group to the amine is a singlet. The signals have almost the same position as in the free iigand, except for those of the pyridine hydrogen atoms which have been shifted downfield slightly. This behaviour contrasts with that observed for the corresponding Schiffbase ligand, which in the same solvent releases the metal ion slowly [2]. indicating that the increase in flexibility of the ligand leads to a more stable complex in the medium used. The 'H NMR spectra of the [LaL ~] [NO~ ], complex were recorded immediately after dissolution in (CD~),SO and CD~CN. The spectra were complex and show many signals, suggesting competition between the solvent and the ligand for the lanthanum. This could result in removal of the metal from the macrocycle, behaviour which we have observed already in other systems [ 2,3 l. The IH NMR spectrum for the [ LaL-" I [ C I O , ] , complex was recorded in C D , C N ( Table I ) and shows similar behavtour to that described for the corresponding perchlorate complex with the L ~ macrocycle. There was no change in the spectrum of the complex after ,-- 24 h. This result indicates a greater stability of the lanthanum perchlorate complexes in solution with both ligands. The complexes [LnL ~] [ClOt] ~-xH:O, Ln = C e , Eu and Tb, were examined by cyclic voltammetry at l 0 ~mol dm ~ in 10- ' tool d m - ~ EhNCIO~ in DMF: no oxidation-reduction processes were detected. 3.8. The cr3.'stal struct,,res o f L-" a n d L:H,ICI04I.,
Single crystals of the macrocycle L~" suitable for X-ray analysis were produced by recrystallization in acetonitrile. The crystal structure is shown in Fig. I. The molecular geometry is characterized by a crystallographic mirror plane running through C I 3 and dividing the pyridine ring. The macrocycle is bent with the benzene rings at an angle of 36.7(2) ° to each other. Crystals of composition [C2_-H_~.~N~O_,] [CIO412 were obtained by slow evaporation of an
L. Valencia et al. / hu~rganica Chimica At'ta 282 ¢ 1998,~ 4 2 - 4 9
acetonitrile solution of the [ LaL-" I [ CIO4 I," 3HzO complex. The diprotonated macrocycle is almost symmetrical, as shown in Fig. 2, although in this case there is no crystallographic mirror plane relating both halves of the molecule. The significant difference between the macrocycles lies in the environments of the N atoms of the amino groups. The C - N ( a m i n o ) distances increase on protonation ( C - N ! .371.46 A, and 1.46-1.51 ,~ for L-" and L-'H_, respectively). Also, and perhaps to 'accommodate' the perchlorate ions, the angles formed between the planes of the benzene tings and those of the pyridine ring increase notably ( from 2 i ° to 45°). The perchlorate anions are involved in hydrogen bonding interactions with the NH_, groups ( N ( 8 ) - O ( 1 ! ) 2.90( i ), N ( 8 ) - O ( 2 2 ) 2.93( I ), N ( 2 6 ) - O ( 1 3 ) 2.97(I). N ( 2 6 ) O( 13 ~) 2.91(I) ,$,). In both structures the remaining macrocyclic bond distances and bond angles are within the expected range of values.
4. S u p p l e m e n t a r y material
Further details of the crystal structure determination can be ordered from Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen. under the depository numbers CSD-408134 and CSD-408135 for L-" and L-'t.t, [ CIO+I_, respectively.
Acknowledgements We thank La Xunta de Galicia ( X U G A 20903B96) and {he University of La Corufia for financial support.
References I I1 (a) J.-M. Lehn. Science 227 (1985) 849; (b) J.-M. Lehn, Angew. Chem., Int. Ed. Engl. 27 { 1988) 89. 121 R. Bandin, R. Ba.stida, A. de Bias, P. Castro, D.E. Fenton. A. Mac/as, A. Rodtlguez, T. Rodr/guez-Blas, J. Chem. Soc., Dalton Trans. (1994) 1185. 131 R. Bastida, A. de Bias, P. Ca.~tro, D.E. Fenton, A. Macia.s, R. Rial. A. Rodn'guez, T. Rodr/guez-Blas. J. Chem. So¢.. Dalton Trans.( 19961 1493.
49
| 4 J H. Adamx. R. Ba_~tida. A. de Blab,. M. C a r n o ~ D . E lemon. A+M~ias, A. Rodn'guez. T. Rodn'guez-Blas, Polyhedron 16 {4p (1997) 567. [5l C. Lodeiro, R. Ba~tida, A. de Blas. D.E. lemon, A, Macias. A. Rodn'guez. T. Rodr/gucz-Blas. |norg. Chim. A c ~ 267 { 1998) 55. [6J DE. Fcntou. P.A. Vigato. Chem. Soc. Roy. 17 4"ISr88} 69. 17 ] P.V. Bernhardt.G.A. Lawrance. Coord. Chem. Rev. 104 (1990) 297. |81 P, Guerricro, S. Tamburini. P,A. Vigato, Co<~rd. Chem. Rev. 139 (1995) 17. [91 V. Alexander.Chem. Rev. 95 { 1995) 273. [ tO] MP. Hogerheide, J. Boersma, G. van Koten, Coord. C h c m Rev. I55 { 1996) 87. [ !1 ] EP. Papadoupoulus. A. Jarrar. C.H. Isstdoa'ides. J. Or E. Chem. 31 { 19(:~ ) 615. [ 121 D. J'erchel, J 1 Heider. H. Wagner. Liebigs Ann. Chem. 613 { 1958l 153. 1131 P-A- Taxker. EB. Fleischer, J. Am. Chem, So~. 92 c 1970) 7072. 1141 R.D. Cannon. B. Chiswell, L M . Venanzi. J. Chem. Soc. A t 1967) 1277. ! 151 D.E. Fenton. BP. Murphy. A.J. Leong [..F. Lindoy, A. Bashall, M. McPartlin, J. Chem. Sot:., Dalton Trans. (1987) 2543. [ 16l Enraf-Nonius. CAD4-Exptess Software, Version 5.1. Enraf-Nonius, Delft, 1995. [ 17l A.L- Spck. H E L E N A . a proffram for data reduction of C A D 4 data., University of Utrecht. Netherlands, 1993. [ 18} N. WMker. D. Stuart,Acta Crystallogr.,Sect. A 39 (1983) 15g 166. [ 19] G.M. Shcldrick. Acta C~stallo~r., Sect. A 4 6 { 1990) 467-473. {20] G+M. Sheldrick,SHELXL93, program for data refinement of cnjstal structures, University of G~lingen, Germany. 1993. 12 ! ] International Tables for X-ray Crystallography, Vol. C, Kluwer, Ootdrecht, Netherland,~. 1995. [ 22 i I a) L. Zsolnai, ZORTEP. a program for the presentation of thermal ellipsoids, University of Heidetberg. Germany, 1994: (b} E. Keller, SCHAKAL 92, J. Appl. Crystallogr. 22 (1989) 19. [23l L H Van Vleck, A. Frank, i~ys. Rev. 34 11929) 494; 34 (1929} 1625. [ 24] M. Mohan. I.P. Tandon, N.S. Gupta, J. lnorg. Nucl. Chem. 43 ( 1981 } 1224. 125 ] F.A. Hart, Comprehensive Coord. Chem. 3 (1987) 1059, Chap. 2. 126l W J . Geary, Coord+ Chem. Rev. 7 { 1971 ) 81. [ 271 N.S. Gill, R.H. Nunal|. D.E Scaife, J. [norg. Nucl. Chem. 18 { 1961 ) 79. [ 28l M.[:. Rosemhal. J. Chem. Educ. 50 (1973) 331. [ 29] A.J. Hathaway, A.E. Underhill+ J. Chem. Soc.( 1961 ) 3091. [ 301 L. De Cola, D . L Smiles. L M . Vallarino, Inorg. Chem. ~ ( 1986} 1729. 131 ] J.-C.G. Biinzli, D. Wessner, Coord. Chem. Rev. 191 (1984) 253. [ 32 ] W+T. Carnall, S. Siegel, J.R. Ferraro, B. Tani, E. GehetL Inorg. Chem. 12 (1973) 560. |33l JR. Fcrraro. J. lnorg. Nucl. Chem. 10 { 1959) 319. [_'14] P. Guerriero, U. Casellato. S. Tamburini, P.A. Vigato. R. Graziani, Inorg. Chim. Acta 129 ( 19~,7 j 127. { 351 N.F. Curtis, Y.M. Curtis, h,otg. Chem. 4 (1965) 804. [36] AB.P. Lever+ E. Mantovani, B.S. Ramaswamy. Can. J. Chem. 44 { 1971 ) 1957.