The crystal structures and spectral behaviour of BENZO-15-CROWN-5 adducts with hydrated lanthanide picrates

PolyhedronVol.

~

15. No 211.pp 3519 3525, 1996 Copyright ~ 1996 Elsevier Sctence Ltd Printed in Great Britain All rights reserved 0277 5:~87 96 $ 1 5 . 0 0 + 0 0 0

Pergamon S0277-5387(96)00084-8

THE CRYSTAL S T R U C T U R E S AND SPECTRAL BEHAVIOUR OF BENZO-15-CROWN-5 A D D U C T S WITH H Y D R A T E D L A N T H A N I D E PICRATES ZHI-XIAN ZHOU,* WEN-CHAO ZHENG and YAN-ZHONG LI Department of Chemistry, Zhengzhou University, Zhengzhou 450052, P.R. China

and ZHI-HUA MAO, ZONG-HUA ZHOU and ZHOU HONG Department of Chemistry, Sichuan University, Chengdu 610064, P.R. China

(Received 8 August 1995 ; accepted2 February 1996) Abstract--A new series of benzo-15-crown-5 adducts with hydrated lanthanide (La, Pr, Nd, Sm, Eu, Gd, Er) picrates has been obtained. Elemental analyses indicated that their stoichiometry is 1:2:3 (metal:benzo-15-crown-5 :picrate) except for the lanthanum adduct. X-ray structural analysis of the Nd, Sm and Er adducts revealed that Nd, Sm or Er ions coordinate directly with water molecules and the picrate anion. The benzo-15crown-5 acts as a second-sphere ligand which associates with the Nd, Sm or Er ion through hydrogen bonding by coordinating water molecules. From investigation of the IR and UV vis spectra of the adducts, it can be deduced that the adducts, except lanthanum, exhibit a similar molecular structure to that of the Nd, Sm and Er adducts. These new adducts may also be classified as supermolecules because each is an associate of two chemical species of hydrated lanthanide picrate and benzo-15-crown-5 held together by coordination water molecules. Copyright ,,~;, 1996 Elsevier Science Ltd

Recently, a large number of transition metal complexes have been shown to enter second-sphere coordination and so form adducts with crown ethers. This second-sphere coordination has undergone rapid development and turned into a fascinating corner of crown ether chemistry, l In the course of our study on the extraction mechanism of lanthanide picrates, Ln(Pic)3, with benzo-15crown-5 (BI5C5), 2 three crystalline complexes, LnPic3"L2"2H20"CH3CN (Ln = Sc, Y, Yb: L = B15C5), have been obtained, and their crystal systems and space groups are triclinic and PT, respectively. X-ray structural analysis disclosed that the Sc, Y or Yb ions do not coordinate directly with the B15C5 molecules, but coordinate to the three bidentate picrate anions and two water mol-

ecules, and the B15C5 molecule virtually acts as a second-sphere ligand which associates with the hydrated scandium, yttrium or ytterbium picrate by hydrogen bonding through coordinating water molecules. 34 These interesting results motivated us to extend our study of the second-sphere coordination of lanthanide crown ether chemistry, so that a new series of B15C5 adducts with hydrated lanthanide picrates (La, Pr, Nd, Sm, Eu, Gd, Er) has been prepared. This paper reports the study of the spectral behaviour of these new lanthanide adducts and the crystal structures of the Nd, Sm and Er adducts.

EXPERIMENTAL

Reagents * Author to whom correspondenceshould be addressed.

All the chemicals were of analytical grade. B15C5 was recrystallized from n-heptane (m.p. 79 80 C).

3519

3520

ZHI-XIAN ZHOU et al.

Hydrated lanthanide picrates were prepared according to the literature method and were stored in a desiccator, s Their general formula is Ln(Pic)3"4H20 by elemental analysis. Preparation o f the adducts

The Er adduct was prepared by dissolving a 1 : 2 molar ratio of hydrated erbium picrate and B 15C5 in a 1 : 1 (v/v) mixed solvent of MeCN and EtOH, and the resulting solutions were filtered and allowed to stand over several days until an orange-red crystalline product of the adduct was separated. A single crystal suitable for X-ray structural analysis was obtained by recrystallization (twice) using the same mixed solvent. The adducts of La, Pr, Nd, Sm, Eu and Gd and the single crystal suitable for X-ray structural analysis were prepared in the same manner except that 1 : 2 : 1 (v/v/v) mixed solvent of MeCN, EtOH and H20 was used instead of the 1 : 1 mixed solvent of MeCN and EtOH. Chemical and physical measurements

Elemental analyses (C, H, N) were performed on a Carlo-Erba 1106 elemental analyser. The lanthanide ion contents were determined by spectrophotometric methods using chlorophosphonazo III as photometric reagent. IR and UV-vis spectra were recorded as Nujol mulls on Shimadzu 435 and Hitachi UV220A spectrometers, respectively. Determination of the crystal and molecular structure

Orange-red transparent crystals with the sizes 0.4 x 0.6 x 0.5 (for Er adduct), 0.3 • 0.7 x 0.4 (Nd adduct) 0.4 x 0.4 x 0.3 mm 3 (Sm adduct) were used for the measurement. The intensity data were collected on an Enraf-Nonius CAD4 diffractometer with graphite-monochromized Mo-K~ radiation using the e~--20 scan mode. A total of 6079 (9029 for Nd, 9823 for Sm) reflections were collected in the range o f 2 ~ < 0 ~ < 2 0 ~ (2~<0~<23 ~) in which 3959 (6950 for Nd, 6808 for Sm) unique reflections with I >/3a (/) were used in the measurements and refinements. All the data were subjected to correction for Lp factors and for absorption based on the ~ scan technique. All calculations were performed on a PDP11/44 computer using the SDP program package. The coordinates of Er (Nd, Sm) atoms were obtained by analysis of Patterson functions. The coordinates of other non-hydrogen atoms were found on difference maps. Atomic coordinates and anisotropic temperature factors for all non-hydrogen atoms

were refined by a full-matrix least-squares procedure to a discrepancy factor of R = 0.049, and Rw = 0.056 (Nd crystal, R -- 0.034, Rw = 0.076; Sm crystal R = 0.053, Rw = 0.056). R E S U L T S AND D I S C U S S I O N The analytical data (Table 1) show that the adducts have the composition Ln(Pic)3.L2.nH20 (L = B15C5, n = 4-7) indicating that the ratio of B15C5 : LnPic3 is 2:1 except for the lanthanum adduct. The adducts exhibit an orange-red colour distinct from the yellow colour of the hydrated lanthanide picrates. The IR spectra of the adducts revealed that the molecular symmetric vibrational absorption of the ligand at ca 980 cm -1 disappears and that the v ( A r - - O - - C ) absorption at 1230 cm -1 shifts to 1207 cm -1 and 1211-1214 cm -1 for adducts 1 and 2-7, respectively. These results indicate that the interaction between B15C5 and lanthanide ions exists, and the obviously broad absorption peaks appearing at 3200-3500 cm -1 are consistent with those of the analytical results (Table 1). The crystallographic data for the Nd, Sm and Er adducts and selected bond lengths and angles are given in Tables 2 and 3, respectively. The molecular structures of the Nd, Sm and Er adducts are shown in Figs 1, 2 and 3, respectively. It is quite interesting to note that the Nd, Sm and Er adducts include the B15C5 molecules, but the Nd, Sm or Er ion coordinates directly with the water molecules and one picrate anion, and the latter acts as a bidendate donor agent attaching the lanthanide ions through phenolic oxygen and one of the nitro oxygen atoms. This means that the coordination number of Nd, Sm and Er in the adducts is 9, 9 and 8, respectively, as shown in Figs l, 2 and 3. As a matter of fact, the two B15C5 molecules act as second-sphere ligand located on either side of hydrated lanthanide picrate. Based on the minimum bond lengths between the oxygen atoms of B15C5 and the coordination water molecules, which are summarized in Table 4 for Nd, Sm and Er adducts, it may be deduced that the B15C5 molecules associates with Nd, Sm and Er ions through hydrogen bonding of coordinating water molecules. The other two picrate anions, which also act as bidentate donors, take a similar mode to the B15C5 molecules to associate with Nd, Sm or Er ion, through hydrogen bonding of coordinating water molecules. The minimum bond lengths (A) between the oxygen atom of the nitro or phenolic groups and the coordinating water molecules are listed in Table 4. Bourgoin et al. 6 reported that J'rnax for the Pic

Structure and behaviour of benzo-15-crown-5-Ln(Pic)3 adducts

3521

Table 1. Analytical data for the title adducts* Found (calc.) (%) Adduct LaPi% 9L" 4H20 PrPic3 9L," 5H20 NdPic3 9L~" 7H20 SmPic3 9L2" 7H20 EuPic3 9I.-2 97H20 GdPic3 9L2" 6H20 ErPic3 9L2" 6H20

C

H

N

RE

33.3 (33.7) 37.0 (37.1) 37.8(37.2) 36.7 (36.9) 36.7 (37.3) 36.9 (36.8) 36.8 (36.9)

3.9 (3.9) 4.0 (4.0) 4.0 (4.0) 4.1 (4.0) 4.0 (3.9) 4.0 (4.0) 3.9 (3.9)

11.0 (10.8) 8.6 (8.6) 8.7 (8.4) 8.3 (8.4) 8.3 (8.5) 8.5 (8.4) 8.4 (8.4)

12.0 (11.9) 9.7(9.7) 9.9 (9.7) 10.0 (10.0) 10.3(10.1) 10.3 (10.6) 11.2 (11.2)

*L = B15C5.

Table 2. Crystallographic data for Nd, Sm and Er adducts Formula

C46H60038N9Nd C46H60038N9Sm C46H58037N9Er

Crystal system Formula weight Space group a (/~) b (A) c (A) fl C) V (A 3) Z

Monoclinic 1491.28

Monoclinic 1497.40

Monoclinic 1496.28

P21/c

P21/c

P2j/c

17.536 (2) 14.818 (1) 23.621 (4) 90.74 (1) 6137.3 4

17.560 (4) 14.777 (2) 23.651 (3) 90.8 (1) 6101.8 4

17.546 (2) 14.666 (3) 23.410 (3) 90.2 (1) 6023.7 4

anion of alkali picrate shifts to a longer wavelength on formation of a 1 : 1 contact ion pair of a 1:2 crown-separated ion pair with crown ethers. Our previous study also reached this conclusion. 7"8 On the other hand 2ma, for the Pic anion in the lanthanide picrates was found at 340-342 nm (in a benzene solvent) whereas the adducts between B15C5 and lanthanide picrates appeared at 315324 nm (except La adduct). The pronounced hypsochromic shift, i.e. )~maxfor the Pic anion shifted to shorter wavelength, probably arises from the spatial arrangement of the molecules of the title adducts. As mentioned above, in the Nd, Sm and Er adducts, the two B15C5 molecules act as second-sphere ligands located on either side of the hydrated lanthanide picrate which associates with the Nd, Sm or Er ion through hydrogen bonding of coordinating water molecules. This implies that the interactions of Pic anions with the B 15C5 molecules may occur. As a result, delocalization of the electrons of the Pic anion decreases and )'maxshifts to shorter wavelength. Trivalent lanthanide ions have a 4f"5s2p 6 outer shell electronic configuration. In general, the bonds between lanthanide ions and macrocycles are

mainly ion~lipole and non-directional and are similar to those between alkali metal ions and crown ethers, since the 4f electrons are effectively shielded. 9 In the case of the Nd, Sm and Er adducts, X-ray structural analysis revealed that the B15C5 molecules take a special association mode, i.e. through hydrogen bonding of coordinating water molecules to combine with the Nd, Sm or Er ion as shown in Figs 1, 2 and 3. It can be deduced that the coordination behaviour of the water molecules or Pic anion with lanthanide ions is stronger than that of B15C5 molecules, and, therefore, the hydrated lanthanide picrate, rather than the lanthanide crown ether cationic complex, is formed predominately. Owing to the steric hindrance of the bulky Pic anion and crowding by coordinating water molecules around the Nd, Sm or Er ion, the cavity of B15C5 cannot accommodate the Nd, Sm or Er ion directly. Consequently, the B15C5 molecules takes on a special association mode in order to combine with them. It is obvious that the title adducts conform to a 1 : 2 lanthanide ions to B15C5 stoichiometry (except for the La adduct). The investigation of IR and UV-vis spectra of the title adducts (except La

3522

ZHI-XIAN ZHOU et

al.

Table 3. Selected bond distances (A) and bond angles (~ Er(Pic)3 92B15C5" 6HzO Er--O(wl) 2.335(7) Er--O (w4) 2.320(9) Er--O(11) 2.259(7) O(wl)--Er--O(w2) O(wl)--Er--O(w5) O(wl)--Er--O(17) O(w2)--Er--O(w5) O(w2)--Er--O(17) O(w3)--Er--O(w6) O(w4)--Er--O(w5) O(w4)--Er--O(17) O(w5)--Er--O(17) O(11)--Er--O(17)

71.1(3) 81.3(3) 74.4(3) 97.4(4) 85.6(3) 137.9(3) 95.6(4) 95.4(3) 153.2(3) 66.3(3)

Er--O(w2) Er--O (w5) Er--O(17)

2.335(8) 2.297(9) 2.498(9)

O(wl)--Er--O(w3) O(wl)--Er--O(w6) O(w2)--Er--O(w3) O(w2)--Er--O(w6) O(w3)--Er--O(w4) O(w3)--Er--O(1 I) O(w4)--Er--O(w6) O(w5)--Er--O(w6) O(w6)--Er--O(11)

135.1(3) 70.0(3) 78.0(3) 140.3(3) 79.3(3) 69.5(3) 69.4(3) 84.5(4) 124.7(4)

Nd(Pic)3 92B15C5 97H20 Nd--O(wl) 2.466(7) Nd--O(w4) 2.479(8) Nd--O(w7) 2.498(8)

Nd--O(w2) Nd--O(w5) Nd--O(11)

O(wl)--Nd--O(w2) O(wl)--Nd--O(w5) O(wl)--Nd--O(11) O(w2)--Nd--O (w4) O(w2)--Nd--O(w7) O(w3)--Nd--O(w4) O(w3)--Nd--O(w7) O(w4)--Nd--O(w5) O(w4)--Nd--O(11) O(w5)--Nd--O(w7) O(w6)--Nd--O(w7) O(w7)--Nd--O(11)

O(wl)--Nd--O(w3) O(wl)--Nd--O(w6) O(wl)--Nd--O(17) O(w2)--Nd--O (w5) O(w2)--Nd--O(11) O(w3)--Nd--O(w5) O(w3)--Nd--O(11) O(w4)--Nd--O(w6) O(w4)--Nd--O(17) O(w5)--Nd--O(11) O(w6)--Nd--O(11) O(w7)--Nd--O(17)

137.1(3) 132.0(3) 71.2(3) 141.1(3) 67.7(3) 79.0(3) 70.2(3) 70.8(3) 67.3(3) 112.8(3) 134.2(3) 120.8(3)

2.472(7) 2.514(10) 2.392(6)

Sm(Pic)3 92B15C5" 7H20 Sm--O (w1) 2.431 (6) Sm--O(w2) 2.434(7) Sm--O(w3) 2.456(6)

Sm--O(w4) Sm--O(w5) Sm--O(w6)

O(wl)--Sm--O(w2) O(wl)--Sm--O(w3) O(wl)--Sm--O(w4) O(wl)--Sm--O(w5) O(wl)--Sm--O(w6) O(w 1)--Sm--O(w7) O(wl)--Sm--O(11) O(wl)--Sm--O(17) O(w2)--Sm--O(w3) O(w2)--Sm--O(w4) O(w2)--Sm--O(w5) O(w2)--Sm--O(w6)

O(w2)--Sm--O(w7) O(w2)--Sm--O(11) O(w2)--Sm--O(17) O(w3)--Sm--O(w4) O(w3)--Sm--O(w5) O(w3)--Sm--O(w6) O(w3)--Sm--O(w7) O(w3)--Sm--O(a 1) O(w3)--Sm--O(17) O(w4)--Sm--O(w5) O(w4)--Sm--O(w6) O(w4)--Sm--O(w7)

137.5(2) 67.8(2) 70.2(2) 140.8(3) 72.5(2) 102.9(3) 124.6(3) 72.6(3) 70.7(2) 142.6(2) 80.8(3) 133.7(3)

adduct) showed that they have similar bathochromic and hypsochromic shifts compared with the free ligand and corresponding lanthanide picrates, respectively. Since the trivalent lanthanide

70.3(3) 143.3(3) 84.7(3) 74.4(3) 125.1(3) 67.0(4) 131.9(3) 82.5(3) 130.4(3) 126.4(3) 72.2(3) 70.1(3)

2.435(7) 2.419(8) 2.471 (8) 70.9(3) 71.3(3) 84.9(3) 134.7(2) 143.0(2) 111.7(2) 70.2(3) 121.4(3) 70.1 (3) 82.0(2) 69.9(3) 136.7(3)

Er--O(w3) Er--O (w6)

2.351(9) 2.346(9)

O(wl)--Er--O(w4) O(wl)--Er--O(11) O(w2)--gr--O(w4) O(w2)--Er--O(11) O(w3)--Er--O(w5) O(w3)--gr--O(17) O(w4)--Er--O(11) O(w5)--Er--O(11) O(w6)--Er--O(17)

Nd--O(w3) Nd--O(w6) Nd--O(17)

139.4(3) 130.5(3) 148.5(3) 76.9(3) 71.0(3) 135.3(3) 74.8(4) 140.4(3) 76.6(3)

2.514(9) 2.471 (8) 2.644(9)

O(wl)--Nd--O(w4) O(wl)--Nd--O(w7) O(w2)--Nd--O(w3) O(w2)--Nd--O(w6) O(w2)--Nd--O(17) O(w3)--Nd--O(w6) O(w3)--Nd--O(17) O(w4)--Nd--O(w7) O(w5)--Nd--O(w6) O(w5)--Nd--O(17) O(w6)--Nd--O(17) O(11)--Nd--O(17) Sm--O(w7) Sm--O(11) Sm--O(17)

80.8(3) 70.3(3) 102.8(3) 70.0(3) 73.3(3) 137.3(3) 138.2(3) 143.1(3) 70.6(3) 143.0(3) 81.8(3) 63.1(3) 2.481 (9) 2.368(8) 2.607(10)

O (w4)--Sm--O (11) O(w4)--Sm--O(17) O(w5)--Sm--O(w6) O(w5)--Sm--O(w7) O(w5)--Sm--O(11) O(w5)--Sm--O(17) O(w6)--Srn--O(w7) O(w6)--Sm--O(11) O(w6)--Sm--O(17) O(w7)--Sm--O(11) O(w7)--Sm--O(17) O(11)--Sm--O(17)

71.5(3) 81.9(3) 72.2(3) 78.6(3) 67.6(3) 131.2(3) 67.5(3) 126.9(3) 140.8(3) 132.3(3) 138.5(4) 63.6(3)

ions closely resemble one another chemically and physically, it can be confirmed that the molecular structure of the title adducts (except La) is similar to that of the Nd, Sm or Er adduct, i.e. B15C5 acts

3523

Structure and behaviour of benzo-15-crown-5-Ln(Pic)3 adducts C'{"4m)

C(4J)

C(4| )

)0(25) 0(24) C(25)

~r

Cy4e)

C(23) (

0(26)

~C(4d)

?0(wl)

X 21)

C(22

0(w3)

/

0( ] 3)

12)~

(XwT)

N(

0(21)

13)

0(23)

0(14)

0(35) 0(~)

0(w2>

n,, ~ *

N(32)

O<5

.

CY5e )

C~5g)

v 0(33)

~,~ C(5j)

cx 5i)

C
Fig. I. Molecular structure of Nd(Pic)3" 2B15C5" 7H20.

0(51) f _

~

C(5t) ~ 0 ' ( 5 2 ) C(5)H

O(15)

~'(5a)

C(Sb~

0(55)

N(14)1

0(16) C<15)

C(Sin)

0(14)

IC(5n)

K53~

C( 5kl

0(17)

0(w2)

(~ 13) 4d)

C~4e)

0(33) O(31) N( 3~

N(

12

0(12

C( 33)(I C(36)A,,f.~

~ f

i |~l~

~J I

~(4b)

0(41) C(4al

0(34)

N(34)

O(w5)

0(35)

C(4n) 0(21)

0(24)

0(w6) C(4i)~

C(21) 4j)

0( 43)I (26)

0(26),

26)•0(27)

l

1

0(44)

~.IC(41) C~4k)

Fig. 2. Molecular structure of Sm(Pic)3-2B15C5" 7H20.

3524

ZHI-XIAN ZHOU et al. 4c)

C(4l)

0(14)

a 4k~6..A

,~zs~ a25)

I~

/

....

.....

a2s~

I

O(15)

H(2

~26;,

O(26)

'0(w4) ~

~

t6)

15) a5b)

IX 17)

CXSc)

[51) (

0(23)

54)

C(3:

a5j)

C(34 (.'(33) 0(35)

II~ 33)

Fig. 3. Molecular structure of Er(Pic)3" 2B15C5" 6H20.

Table 4. The minimum bond lengths (A) between the oxygen atom of B 15C5 nitro or phenolic groups and coordinating water molecules Nd adduct O(wl)--O(44) O(wl)--O(43) O(w6)--O(55) O(w6)--O(53) O(w7)--O(42) O(w2)--O(31) O(w2)--O(32) O(w4)--O(21) O(w4)--O(26) O(w5)--O(34) O(w7)--O(31)

Sm adduct 2.957 2.664 2.808 2.925 2.704 2.656 2.908 2.627 2.832 2.971 2.698

O(wl)--O(42) O(w2)--O(55) O(w2)--O(54) O(w3)--O(52) O(w4)--O(45) O(w7)--O(53) O(wl)--O(31) O(w3)--O(31) O(w5)--O(31) O(w5)--O(22)

as a second-sphere ligand which associates with lanthanide ions through hydrogen bonding of coordinating water molecules. The title adducts may also be classified as a supermolecule because each adduct is an association with two chemical species of hydrate lanthanide picrate and B 15C5 molecules held together by coordinating water molecules. 1~ O f the title adducts, the La adduct exhibits unusual characters, and the study of its molecular and crystal structure will be reported later. Acknowledgement--We thank the National Natural

Er adduct 2.770 2.990 2.865 2.750 2.822 3.072 2.675 2.703 2.693 2.843

O(wl)--O(52) O(w2)--O(54) O(w2)--O(55) O(w4)--O(43) O(w4)--O(44) O(w6)--O(42) O(wl)--O(31) O(w3)--O(21) O(w3)--O(26) O(w5)--O(21) O(w6)--O(31)

2.754 2.827 2.813 2.792 2.904 2.726 2.658 2.596 2.797 2.749 2.657

Science Foundation of China for financial support of this work.

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Structure and behaviour of benzo-15-crown-5-Ln(Pic)3 adducts Kai-bei Yu and Zhong-Yuan Zhou, Yingyong Huaxue 1993, 10(6), 31. 4. Zhi-Hua Mao, Zong-Hua Zhou, Zhou Hong, ZhiXian Zhou, Jian-Wei Li and Chen-Xia Du, Sichuan Daxue Xuebao (Ziran Kexue Ban) 1995, 32(3), 319. 5. Yong-Chi Tian, Ying-Qiu Liang and Jia-Zan Ni, Chem. J. Chin. Univ. 1988, 9(8), 113. 6. M. Bourgoin, K. H. Wong, J. Y. Hui and J. Smid, J. Am. Chem. Soc. 1975, 92, 3462.

3525

7. Xian-Xin Zhang and Zhi-Xian Zhou, Chem. J. Chin. Unit'., Engl. Edn. 1989, 5, 224. 8. Zhi-Xian Zhou, Ying-Xia Zhou, Yan-Zhong Li and Kui-Ling Ding, Polyhedron 1995, 20-21, 3033. 9. Gin-Ya Adachi and Yoshiyuki Hirashima, Cation Binding by Macrocycles, p. 701. Marcel Dekker, New York (1990). 10. Jean-Marie Lehn, Angew. Chem., Int. Ed. Eng. 1988, 27, 89.