Structural and Spectroscopic Investigations of the 1:1 Complex between Europium Nitrate and a Tetraoxadiaza Macrocycle

Abstract

The crystal and molecular structure of dinitrato( 1,7,10,16-tetraoxa-4,13-diazacyclooctadecane)europium(III) nilratc, ( [ E U ( N~, )~( C~~H~~N~O~) ] N O~) has been determined from single-crystal X-ray diffraction: u = 12.567(3), h = 11.585(3), c = 16.354(5) A, = 112.45(2)", space group P21/n, Z = 4. The structure consists of discrete dinitrato complcx cations and of nitrate anions. The Eu(ll1) ion is 10-coordinate, bonding to the six donor atoms of the macrocyclc and to four 0-atoms of the two bidentate nitrates. Introduction. -Synthetic ionophores are being increasingly used to study the coordination chemistry of lanthanide ions [2] [3]. The 18-membered ligand 1,7,10,16-tetraoxa-4,13-d1azacyclooctadecane (2,2) is the basic unit of a class of tricyclic compartmental cryptands used to bind organic [4] or metal [5] cations. The presence of the two amine groups has a stabilizing influence, and lanthanide complexes with this ligdnd are approximately three orders of magnitude more stable than corresponding complexes with the cyclic hexaether 18-crown-6 [2] (1,4,7,10,13,16-hexaoxacyclooctadecane). No structural data are available for lanthanide coronates with the ligand (2,2), and it is not known if these compounds are simple neutral 1 : 1 complexes, or if they contain cationic species of the type [LnX,L]+ similar to those observed in complexes of 18-crown-6 ether with lanthanide nitrates [6] [7] or chlorides [8].As part of our work on macrocyclic complexes, we report the crystal structure determination of the 1 :I complex between europium(II1) nitrate and the ligand (2,2), along with a discussion of the nitrate vibrational modes.The use of trivalent lanthanide ions to probe the metal-ion binding sites of ionophores is well-established [2], particularly in conjunction with laser-luminescence techniques. To set a basis for further studies on dinuclear cryptands [ 5 ] , we also report the low-temperature emission spectrum of the complex with ligand (2,2). HELVETICA CHIMICA A C r A Vol. 69 (1986) 289 Experimental. -Preparation o/ E u ( N 0 , 1 3 . (2,Z). The complex was prepared in anh. MeCN as described in [9]. using Kryptofix 22 from Merck. Suitable monocrystals were grown by slow evaporation of an MeCN soh. Their composition and purity were ascertained by elemental analysis.Spectroscopic Meusurements. IR spectra were obtained as nujol mulls and KBr pellets with a Perkin-Elmer model 577 and an IFS-113u Bruker E'T-IR spectrometers. Rumun spectra of powdered samples were recorded on a Rumulog-4 spectrometer from Spex Indusfries Inc. Luminescence spcctra of polycrystalline samples (296,77, and 4 K ) and of MeCN solns. (296 K) were recorded o n a laser spectrofluorimeter described in [lo]. Conductivity measurements were obtained with a Metrohm E-365B conductometer equipped with an EA-655 cell; the H,O content of the MeCN solns. was lower than 60 ppm, corresponding to less than 2-3 molecules of H,O per ELI''. C'ollection (?[/he X-Ray Difj+action Dutu. A crystal of dimension 0.26 x 0.27 x 0.22 mm was sealed under Ar atmos...

Photophysical and Structural Impact of Phosphorylated Anions Associated to Lanthanide Complexes in Water

“…The coordination of the NO 3 - anion leads to a more asymmetrical [Eu L B (NO 3 )] complex which displays elongated Eu−N 1 and Eu−N 5 “bonds” (2.9 Å) and a somewhat shorter Eu−N4 bonds (2.3 Å). The NO 3 - anion is bound in a bidentate mode as found in related europium−nitrate complexes (Figure S1). We observe the nonequivalence of the two Eu−O L distances (2.7 and 2.3 Å), which bracket the Eu−O NO 3 distance (2.5 Å).…”

Examination of Structure and Bonding in 10-Coordinate Europium and Americium Terpyridyl Complexes

“…The volume of the europium compound is smaller than that of the terbium compound; however, the ionic radius of europium is calculated to be larger than that of terbium. Placherel et al previously calculated the ionic radius of 10-coordinate europium to be 1.21 Å . When recalculating with the current Shannon ionic radii, the ionic radius for this reported structure is 1.176(4) Å.…”

“…Placherel et al previously calculated the ionic radius of 10-coordinate europium to be 1.21 Å. 33 When recalculating with the current Shannon ionic radii, the ionic radius for this reported structure is 1.176(4) Å. The reported calculation used a currently accurate value of 1.46 Å for the nitrogen atoms; however, 1.31 Å was used for oxygen instead of 1.35 Å.…”

Structural and NMR Characterization of Sm(III), Eu(III), and Yb(III) Complexes of an Amide Based Polydentate Ligand Exhibiting Paramagnetic Chemical Exchange Saturation Transfer Abilities

“…The average Eu−O amide carbonyl and Eu−O ether distances in [Eu L ] 3+ are 2.37 and 2.49 Å, respectively (Table and ). These average bond lengths found in other similar Eu(III) complexes are 2.377 and 2.568 Å, respectively (bond distances range from 2.268 to 2.415 Å and 2.460−2.697 Å, respectively). ,,− This indicates that the Eu(III) complex has a typical carbonyl amide to Eu(III) distance. However, the ether to Eu(III) distance is slightly shorter than what is typically observed.…”