2.3.1 Mononuclear Lanthanide Complexes with β -Diketones
2.3.1.4 Nine-Coordinated Lanthanide Complexes with β -Diketones
H59 C59 C60 H60 N3 O9
Figure 2.23 Molecular ladder of complex Eu(L42)3(DPEPO) involvingπ· · ·πinteractions (C4-C9) and intermolecular hydrogen bonding interactions (C59-H59· · ·O9, C60 – H60· · ·N3), when viewed along the direction of thec-axis [51c]. (Reprinted with permission from S. Biju, M.L.P. Reddy, A.H. Cowley and K.V. Vasudevan, “Molecular ladders of lanthanide-3-phenyl-4-benzoyl-5- isoxazolonate and bis(2- (diphenylphosphino)phenyl) ether oxide complexes: the role of the ancillary ligand in the sensitization of Eu3+and Tb3+luminescence,’’Crystal Growth and Design,9, 3562–3569, 2009. © 2009 American Chemical Society.)
O3
O6 O5
O7 O8
O2 O4 O1
Eu1
Figure 2.24 Asymmetric unit of Eu(L17)3(DDXPO): thermal ellipsoids drawn with 30% probability, H atoms, and non-coordinated solvent molecules omitted for clarity [34]. (Reproduced from D.B.A. Raj, S.
Biju and M.L.P. Reddy, “4,4,5,5,5-Pentafluoro-1-(9H-fluoren-2-yl)-1,3-pentanedione complex of Eu3+
with 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene oxide as a promising light-conversion molecular device,’’Dalton Transactions,36, 7519–7528, 2009, by permission of the Royal Society of Chemistry.)
[Nd(L3)4(H2O)]−complexes (see Figure 2.30) and two TTF−CH=CH−Py·+radical cations (drawn as balls and sticks in Figure 2.30). Each Nd(III) ion is surrounded by nine oxygen atoms from four bis-chelating L3ligands and one water molecule. The coordination geometry of the Nd(III) ions is a distorted capped square antiprism. The [Nd(L3)4(H2O)]−complex, related through the inversion center, forms pseudo-dimeric units with strong hydrogen bonds between the water molecules and oxygen atoms of the L3anions.
Among the fluorinatedβ-diketones reported, the hexafluorinated 1,1,1,5,5,5-hexafluoro- 2,4-pentanedione (HL3) ligand was found to have a tendency to form a nine-coordinated metal center with distorted monocapped square antiprism coordination polyhedra, while other fluorinatedβ-diketones tend to form ten-coordinated complexes with distorted square antiprism coordination polyhedra. The reasons are twofold. Firstly, owing to the presence of the stronger electron-withdrawing hexafluoroacetyl group on L3, interactions between the central Eu(III) ion with the oxygen atom of the nearby hexafluoroacetyl group become weaker than those occurring in the complexes of thenoyltrifluoroacetonate (HL5) and 4,4,4-trifluoro-1-phenyl- 1,3-butanedionate (HL6), leading to longer Eu–O bonds, as observed. Secondly, a larger ligand–
metal separation (the longer Eu–O bonds) reduces steric hindrance around the lanthanide ion as compared with the complexes with other fluorinatedβ-diketones, making the accommodation of additional solvent molecules of water and ethanol facile. De Silvaet al. [26b] reported
O5 O6
O3
O7 O8
O4
O1 O2 Eu1
Figure 2.25 Asymmetric unit of Eu(L17)3(DPEPO): thermal ellipsoids drawn with 30% probability, H atoms, and non-coordinated solvent molecules omitted for clarity [34]. (Reproduced from D.B.A. Raj, S. Biju and M.L.P. Reddy, “4,4,5,5,5-Pentafluoro-1-(9H-fluoren-2-yl)-1,3-pentanedione complex of Eu3+
with 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene oxide as a promising light-conversion molecular device,’’Dalton Transactions,36, 7519–7528, 2009, by permission of the Royal Society of Chemistry.)
the crystal structure of nine-coordinated [Eu(L3)3(dmphen)(EtOH)] (dmphen=2,9-dimethyl- 1,10-phenanthroline) (Figure 2.31), which is in contrast with the structure of eight-coordinated Eu(L5)3(dmphen) (see Figure 2.32). It is interesting to note that a molecule of non-coordinating dmphen is found in the solid state, and is involved inπ–πinteractions with the coordinated neutral ligand. The aromatic interplanar separation is 3.301–3.429◦Å.
Malandrino et al. [72] recently reported two new neodymium metal organic chemi- cal vapor deposition precursors, the Nd(L3)3·monoglyme·H2O and the Nd(L3)3·diglyme [monoglyme=(dimethoxyethane) and diglyme=(bis(2-methoxyethyl)ether)] with the crystal structures of the former being shown in Figure 2.33. The two complexes are both nine- coordinated by six oxygen atoms of three L3anions and by three oxygen atoms of a diglyme molecule or a monoglyme and a water, with the former complex having two coordination geometries of a distorted capped square antiprism and a distorted tricapped trigonal prism, and the latter complex being a monocapped square antiprism. They have applied Nd(L3)3·diglyme for the MOCVD (metal organic chemical vapor deposition) fabrication of NdBa2Cu3O7−δ
films on MgO substrates.
O6 O4 O1
O2 O3 Nd1 O5 N1
N2
Figure 2.26 Structure of the complex Nd(L34)3(phen) as viewed down the square face of a square-antiprismatic coordination polyhedron of Nd(III) center (50% probability ellipsoids, H atoms, co-crystallized solvent molecules, and phenyl groups of the 1,3-diketonato ligands omitted) [44]. (Repro- duced with permission from N.M. Shavaleev, R. Scopelliti, F. Gumy and J.C.G. Bunzli, “Visible-light excitation of infrared lanthanide luminescence via intra-ligand charge-transfer state in 1,3-diketonates containing push-pull chromophores,’’European Journal of Inorganic Chemistry, 2008,9, 1523–1529.
© Wiley-VCH Verlag GmbH & Co. KGaA.)
Na1 Ow
O13 O11
O8
O12 O14
Tb1
Figure 2.27 ORTEP diagram of [Na(DB18C6)H2O][Tb(L58)2] with the thermal ellipsoids drawn at the 30% probability level and the hydrogen atoms removed for clarity [59]. (Reprinted with permission from P.N. Remya, S. Biju, M.L.P. Reddy, A.H. Cowley and M. Findlater, “1D Molecular ladder of the ionic complex of terbium-4-sebacoylbis(1-phenyl-3-methyl-5-pyrazolonate) and sodium dibenzo-18-crown-6:
synthesis, crystal structure, and photophysical properties,’’Inorganic Chemistry,47, 7396–7404, 2008.
© 2008 American Chemical Society.)
N420 N410
N412
N414 O22
O24O32 O34 O14 O12
Eu1 N48
N41
Figure 2.28 An ORTEP view of the crystal structure of Eu(L5)3(TPTZ) with partial atomic label- ing. Thermal ellipsoids are drawn at the 50% probability level [25]. (Reprinted fromPolyhedron, 26, C.R. De Silvaa, J.R. Maeyera, A. Dawsona and Z. Zheng, “Adducts of lanthanideβ-diketonates with 2,4,6-tri(2-pyridyl)-1,3,5-triazine: synthesis, structural characterization, and photoluminescence studies,’’ 1229–1238, 2007, with permission from Elsevier.)
N(412) N(48) N(424) N(410)
N(418) N(41)
O(24) O(22) O(34)
O(14) O(32) O(12)
Eu(1)
Figure 2.29 The TPTZ ligands stack to form a centrosymmetric “dimer’’ in the crystal structure of Eu(L5)3TPTZ. [25]. (Reprinted fromPolyhedron, 26, C.R. De Silvaa, J.R. Maeyera, A. Dawsona and Z. Zheng, “Adducts of lanthanideβ-diketonates with 2,4,6-tri(2-pyridyl)-1,3,5-triazine: synthesis, structural characterization, and photoluminescence studies,’’ 1229–1238, 2007, with permission from Elsevier.)
S6 S8
C58 C57
S5 S7
O17
O15 O16 O13
O14
O3 O2 O1
S4 S2
S1
S3 C24
C23
O8 O7
O9W O4
O6 O5
Nd1 N1
O13 O12 O18W O10
N2 Nd2
Figure 2.30 Representation of the asymmetric unit of {[Nd(L3)4(H2O)][(TTF−CH=CH−Py+)]}2. The radical cation donors are drawn as balls and sticks; the paramagnetic anionic coordination com- plexes of Nd(III) are drawn as capped sticks [23d]. (Reprinted with permission from F. Pointillart, O. Maury, Y. Le Gal, S. Golhen, O. Cador and L. Ouahab, “4-(2-Tetrathiafulvalenyl-ethenyl)pyridine (TTF−CH=CH−py) radical cation salts containing poly(β-diketonate) rare earth complexes: synthe- sis, crystal structure, photoluminescent and magnetic properties,’’Inorganic Chemistry,48, 7421–7429, 2009. © 2009 American Chemical Society.)
N3 N4
N1 N2
O5 O6 O1 O7 O4
O2 O3
Eu1
Figure 2.31 Molecular structure of Eu(L3)3(dmphen)(EtOH)dmphen. (Displacement ellipsoids for non- H atoms are shown at the 50% probability level and H atoms are represented by circles of arbitrary size) [26b]. (Reprinted fromInorganica Chimica Acta, 360, C.R. De Silva, J.R. Maeyer, R. Wang, G.S. Nichol, Z. Zheng, “Adducts of europiumβ-diketonates with nitrogen p,p’-disubstituted bipyridine and phenanthroline ligands: Synthesis, structural characterization, and luminescence studies,’’ 3543–
3552, 2007, with permission from Elsevier.)
O52
O51 O53
O54
EU2 O56
N51N52 O55
Figure 2.32 An ORTEP view of the crystal structure of Eu(L5)3(dmphen) with partial atomic label- ing. Thermal ellipsoids are drawn at the 50% probability level [26b]. (Reprinted fromInorganica Chimica Acta,360, C.R. De Silva, J.R. Maeyer, R. Wang, G.S. Nichol, Z. Zheng, “Adducts of europiumβ- diketonates with nitrogen p,p’-disubstituted bipyridine and phenanthroline ligands: Synthesis, structural characterization, and luminescence studies,’’ 3543–3552, 2007, with permission from Elsevier.)
O4A O8A
O4B O3B
O1B
O7B O8B
O6B
O5B O2B O1WB O7A Nd1B
O1A O3A O2A
O5A O6A
O1WA
Nd1A
Figure 2.33 ORTEP view of the two independent molecules in the asymmetric unit of Nd(L3)3· monoglyme·H2O (ellipsoid probability 30%). Fluorine and hydrogen atoms have been omitted for clarity [72]. (Reprinted fromInorganica Chimica Acta,362, R.L. Nigro, R.G. Toro, M.E. Fragalà, P. Rossi, P. Dapporto and G. Malandrino, “Neodymiumβ-diketonate glyme complexes: Synthesis and charac- terization of volatile precursors for MOCVD applications,’’ 4623–4629, 2009, with permission from Elsevier.)
N4 O8 N5
O3 O1
O9 O7 N3
N1
O2
OW O4
O5
O6 N2 Eu1
Figure 2.34 ORTEP diagram of the asymmetric unit of compound Eu(L42)3·bpy·H2O with thermal ellipsoids drawn at the 50% probability. Hydrogen atoms omitted for clarity [73]. (Reproduced from S. Biju, D.B.A. Raj, M.L.P. Reddy, C.K. Jayasankar, A.H. Cowley and M. Findlater, “Dual emission from stoichiometrically mixed lanthanide complexes of 3-phenyl-4-benzoyl-5-isoxazolonate and 2,2’- bipyridine,’’Journal of Materials Chemistry,19, 1425–1432, 2009, by permission of the Royal Society of Chemistry.)
As the very similar coordination ability of lanthanide ions provides a good opportunity for accurately mixing two types of lanthanide ions to make one complex, accordingly result- ing in dual emissions, Reddy and coworkers [73] prepared three new stoichiometrically mixed lanthanide complexes of Sm1/2Eu1/2(L42)3·bpy·H2O, Sm1/2Tb1/2(L42)3·bpy·H2O, and Eu1/2Tb1/2(L42)3·bpy·H2O (bpy=2,2-bipyridine). The crystal structure studies showed that Eu(L42)3·bpy·H2O (see Figure 2.34) is a nine-coordinated mononuclear complex with the coor- dination polyhedron of a distorted monocapped trigonal prism, in which six coordination atoms come from three bidentate L42ligands, two from a bidentate bipy ligand, and one from a water molecule. There are many interestingπ–π, interplanar, and intermolecular hydrogen-bonding interactions in the crystal. Their results indicated that the luminescent intensity can be enhanced and better quantum yields obtained by addition of a controlled amount of a second, carefully selected lanthanide. The dual emissions observed, particularly those of the mixed lanthanide systems, should find applications in the field of organic light emitting diodes (OLEDs).