Because Schiff’s base (or imine) complexes have often been used for the design of metallomesogens, and because the trivalent lanthanides are known to form complexes with these ligands, it was expected that Schiff’s bases could be used to prepare lanthanidomesogens. Whereas the major part of the Schiff’s base metallomesogens described in the literature are complexes of N-aryl substituted salicylaldimines, lanthanide complexes of this type of ligands are more difficult to synthesize in comparison with theN-alkyl substi- tuted salicylaldimines (Fig. 25). For this reason, most Schiff’s base lanthani- domesogens described in the literature haveN-alkyl substituted ligands. The
Schiff’s base complexes reported in 1991 by Galyametdinov and coworkers were the first examples of calamitic (rod-like) lanthanidomesogens (Galya- metdinov et al., 1991). In a very short, yet seminal paper, the authors describe the synthesis and thermal behavior of lanthanide complexes of anN-alkyl sal- icylaldimine ligand L1H (CnH2nþ1¼C7H15, CmH2mþ1¼C12H25). The stoi- chiometry of the complexes was believed to be [RL3X2], but this formula does not lead to an electrically neutral complex. No base was used to depro- tonate the ligand for complex formation. The ligand exhibits a nematic phase.
The lanthanide complexes form a highly viscous smectic mesophase, which was later identified as a smectic A phase (Table 2). Much lower transition
H2n+1CnO
O O
OH
N CmH2m+1 H2n+1CnO
OH
N N
HO
H2n+1CnO OCnH2n+1
OH
OCnH2n+1 N N
N N
OH HO OCnH2n+1 H2n+1CnO
H2n+1CnO
O O
OH
N CmH2m+1
H2n+1CnO OH
N CmH2m+1 O
O O
OH
N CmH2m+1 O
H2n+1CnO
OH N C18H37 C8H17O
OH
N CmH2m+1
OH O
N C10H21 O
O n
L1H
L2H
L3H L4H
L5H
L7H
L6H
L8H2
L9H3
FIGURE 25 Overview of N-alkyl salicylaldimine Schiff’s base ligands.
TABLE 2 Thermal Behavior of Lanthanide Compounds With Two-Ring Schiff’s Base Ligands L1H
Compound CnH2nþ1 CmH2mþ1 Temperatures (C) Reference [La(LH)3(NO3)3] C6H13 C12H25 Cr 70 SmA 184 dec. Binnemans et al.
(2001b) [La(LH)3(NO3)3] C6H13 C18H37 Cr 71 SmA 191 I
(dec.)
Binnemans et al.
(2001b) [La(LH)3(NO3)3] C8H17 C18H37 Cr 66 SmA 199 I
(dec.)
Binnemans et al.
(2001b) [La(LH)2L(NO3)2] C10H21 C12H25 Cr 87 SmA 178 dec. Binnemans et al.
(2001b) [La(LH)2L(NO3)2] C10H21 C18H37 Cr 70 SmA 177 dec. Binnemans et al.
(2001b) [La(LH)2L(NO3)2] C12H25 C12H25 Cr 87 SmA 187 dec. Binnemans et al.
(2001b) [La(LH)2L(NO3)2] C12H25 C18H37 Cr 88 SmA 169 dec. Binnemans et al.
(2001b)
[La(LH)2L(DOS)2] C12H25 C18H37 Cr 113 SmA 132 I Galyametdinov et al.
(1999)
[Pr(LH)2L(NO3)2] C7H15 C12H25 Cr 96 SmA 181 I Galyametdinov et al.
(1991)
[Nd(LH)2L(NO3)2] C10H21 C18H37 Cr 74 SmA 173 dec. Binnemans et al.
(2001b) [Nd(LH)3(NO3)3] C12H25 C12H25 Cr 96 SmA 164 dec. Binnemans et al.
(2001b) [Nd(LH)2L(NO3)2] C12H25 C18H37 Cr 85 SmA 170 dec. Binnemans et al.
(2001b)
[Eu(LH)2LCl2] C7H15 C12H25 Cr 146 SmA 236 I Galyametdinov et al.
(1991)
[Gd(LH)2L(NO3)2] C7H15 C12H25 Cr 98 SmA 192 I Galyametdinov et al.
(1991)
[Gd(LH)2L(DOS)2] C12H25 C18H37 Cr 106 SmA 113 I Galyametdinov et al.
(1999)
[Tb(LH)3(NO3)3] C6H13 C12H25 Cr 75 SmA 172 dec. Binnemans et al.
(2001b)
[Tb(LH)2L(DOS)2] C12H25 C18H37 Cr 106 SmA 126 I Galyametdinov et al.
(1999)
temperatures were observed for complexes with nitrate anions than for com- plexes with chloride counter ions. Exploration of the physical properties of these lanthanidomesogens was hampered by the very high viscosity of the mesophase and by their low thermal stability (in general, they decompose at the clearing point).Binnemans et al.(2001b)prepared homologues of ligand L1H. Depending on the chain length, the ligands exhibit a nematic or a smec- tic C phase. Depending on the ligand or the lanthanide ion, two types of stoi- chiometries were found: [R(LH)3(NO3)3] and [R(LH)2L(NO3)2]. The complexes formed a viscous mesophase, which was identified by XRD as a smectic A phase. The melting point of the complexes was rather low, for one complex even as low as 70C, and the smectic A phase was stable over about 100C (Table 2). However, all the complexes thermally decomposed before the clearing point was reached. Complexes with dodecylsulfate anions had transition temperatures that were 80–100C lower than those of the com- plexes with chloride or nitrate anions, and in this case the complexes cleared without decomposition (Galyametdinov et al., 1999). By placing a second alk- oxy chain on the benzoyloxy group, Bruce and coworkers were able to obtain lanthanide complexes with a hexagonal columnar mesophase (ligand L2H;
Martin et al., 2000). The authors showed that substantially lower transition temperatures could be achieved by selecting triflate anions. The transition temperatures of these complexes were rather low, with the melting point just above 50C and the clearing point just below 90C. The melting and clearing points showed hardly any variation with the lanthanide ion (Table 3).Lode- wyckx et al.(2001)prepared lanthanide complexes of a Schiff’s base ligand with three aromatic rings (L3H, CnH2nþ1¼C6H13, CmH2mþ1¼C18H37).
The influence of the lanthanide ion on the transition temperatures is marginal, although it was found that the nematic phase of the ligand was suppressed, in favor of the smectic C phase. The complexes thermally decomposed before the clearing point was reached. This work shows that the thermal properties of the complexes are largely defined by the Schiff’s base ligands, rather than
TABLE 2 Thermal Behavior of Lanthanide Compounds With Two-Ring Schiff’s Base Ligands L1H—Cont’d
Compound CnH2nþ1 CmH2mþ1 Temperatures (C) Reference
[Dy(LH)2L(NO3)2] C7H15 C12H25 Cr 92 SmA 186 I Galyametdinov et al.
(1991)
[Dy(LH)2L(DOS)2] C12H25 C18H37 Cr 102 SmA 124 I Galyametdinov et al.
(1999) Cr, crystalline phase; SmA, smectic A phase; I, isotropic liquid; dec., decomposition.
by the lanthanide ions. This is different from what is observed for the Schiff’s base ligands with one aromatic ring (vide infra).
The lanthanidomesogens derived of the two-ring or three-ring Schiff’s base ligands are not very suitable for exploration of their spectroscopic, elec- tric or magnetic properties, due to their high transition temperatures, highly viscous mesophases and low thermal stability. It was realized that metallome- sogens with more favorable physicochemical properties were required, other- wise nobody would be interested in this class of LCs. A breakthrough was the discovery of lanthanide Schiff’s base complexes with an enhanced thermal stability and exhibiting a smectic A phase with a relatively low viscosity (Galyametdinov et al., 1994a). The ligands in these complexes are remarkable because they contain only one aromatic ring and because they are not liquid- crystalline themselves (ligandL4H). Mesomorphism is induced by the lantha- nide ion. Such a behavior is quite unique. In general, the mesophase of organic ligands disappears upon complexation, or at least the mesophase is strongly destabilized. Determination of the stoichiometry and the structure of these lanthanidomesogens turned out to be a challenge, since no single crystals suitable for XRD could be obtained at that time. The analytical data for the first reported compounds were in agreement with the stoichiometry [R(LH)2LX2], where LH is the salicylaldimine Schiff’s base, L is its deproto- nated form and X is the counter ion (Galyametdinov et al., 1994a, 1996a).
Thermal analysis data showed the absence of water or ethanol in the com- plexes. The complexes were prepared by reaction of the Schiff’s base ligand with an excess of the lanthanide salt in absolute ethanol. Because the TABLE 3 Thermal Behavior of the Lanthanide Complexes of theN-alkyl-4- (3,4-dialkoxylbenzoyloxy)salicylaldimine Schiff’s Base Ligands L2H Compound CnH2nþ1 CmH2mþ1 Temperatures (C) Reference [Nd(LH)2L(NO3)2] C12H25 C12H25 Cr 84 Colh112 I Martin et al. (2000) [Nd(LH)2L
(CF3SO3)2]
C12H25 C12H25 Cr 57 Colh88 I Martin et al. (2000)
[Gd(LH)2L (CF3SO3)2]
C12H25 C12H25 Cr 51 Colh89 I Martin et al. (2000)
[Tb(LH)2L(CF3SO3)2] C12H25 C12H25 Cr 48 Colh88 I Martin et al. (2000) [Dy(LH)2L(CF3SO3)2] C12H25 C12H25 Cr 51 Colh88 I Martin et al. (2000) [Dy(LH)2L(NO3)2] C12H25 C12H25 Cr 85 Colh146 I Martin et al. (2000) [Er(LH)2L(NO3)2] C12H25 C12H25 Cr 77 Colh128 I Martin et al. (2000) [Er(LH)2L(CF3SO3)2] C12H25 C12H25 Cr 51 Colh88 I Martin et al. (2000) Cr, crystalline phase; Colh, hexagonal columnar phase; I, isotropic liquid.
complexes are insoluble in ethanol—in contrast to the ligand and lanthanide salts—the complexes precipitate upon formation. The complexes can be pur- ified by extensive washing with ethanol, rather than by recrystallization. It was observed that trials to purify the complexes by recrystallization resulted in complexes of lower purity. They are soluble in halogenated organic sol- vents, such as chloroform, dichloromethane, or carbon tetrachloride. The complexes with chloride counter ions have a much lower solubility than the nitrate complexes.
Further work done by the research groups of Galyametdinov, Bruce, and Binnemans gave more insight in the structure of these Schiff’s base com- plexes (Binnemans et al., 1999d, 2000a). By performing the complex forma- tion at temperatures around room temperature, compounds could be obtained with a stoichiometry consistent with [R(LH)3(NO3)3].1H NMR stud- ies on diamagnetic lanthanum(III) complexes showed that in the complexes the Schiff’s base ligand is present in azwitterionic form, that is, the phenolic oxygen has been transferred to the imine nitrogen (Fig. 26;Binnemans et al., 1999d). It was found that the 1H signal corresponding to the imine hydrogen (CH¼¼N) was broadened in the lanthanum(III) complex in comparison with the same signal in the Schiff’s base ligand. In some cases, even a splitting of the imine signal was observed. The value of the coupling constant was of the same order of magnitude as the expected value for a trans-coupling in HC¼¼NþH. The signal atd¼12.29 ppm could be assigned to a NH res- onance and not to an OH resonance by a homonuclear decoupling experiment.
Irradiation of the NH signal led to a collapse of the CH¼¼N doublet. Further evidence for the existence of a zwitterionic form in the metal complexes was given by infrared spectra, and more particularly by the band frequencies of the C¼¼N stretching vibration. The shift to higher wavenumbers in the complexes compared to the corresponding values in the ligands indicated that the nitro- gen atom is not involved in the complex formation and that a C¼¼Nþgroup is present. The best piece of evidence for the type of bonding in the com- plexes are the single crystal X-ray structures of homologous nonmesogenic complexes formed by ligands with short alkyl chains (Fig. 27; Binnemans et al., 2000a; Van Meervelt et al., 2003a,b). The crystal structures show that three Schiff’s base ligands and three nitrate groups are present for each metal ion. The Schiff’s base ligands are in the zwitterionic form, as assumed from the NMR data. The ligands coordinate to the metal ion only via the negatively
H2n+1CnO
O-
N+ CmH2m+1 H
R3+
FIGURE 26 Zwitterionic form of a Schiff’s base ligand coordinating to a rare-earth ionR3þ.
charged phenolic oxygen. No binding occurs between the lanthanide ion and the imine nitrogen, and the three nitrate groups coordinate in a bidentate fash- ion. The coordination number of the lanthanide ion is nine, and the coordina- tion polyhedron can be described as a distorted monocapped square antiprism.
The phenolic proton is transferred to the imine nitrogen, but two of the three transferred protons in the complex form a double hydrogen bond (with the phenolic oxygen and with an oxygen atom of a nitrate group), whereas the third proton only forms a single hydrogen bond (with a phenolic oxygen).
The formation of a zwitterionic form can be rationalized by the tendency of the lanthanide ions to coordinate to negatively charged ligands (with a prefer- ence for O-donor ligands). By transfer of the phenolic proton to the imine nitrogen, the phenolic oxygen becomes negatively charged and can coordinate to the lanthanide ion. TheN-alkyl substituted imine nitrogen has a sufficiently basic character to bind the proton. However, under the same reaction condi- tions, no lanthanide complexes could be obtained withN-aryl Schiff’s bases.
In this type of ligands, the imine nitrogen is probably not basic enough for the uptake of the proton (and thus no zwitterion can be formed). It should been noticed that it is not feasible to deprotonate the Schiff’s base ligand, because in the complexes formed no small inorganic counter ions will be pres- ent and probably they will have an oligomeric or polymeric structure.
O5 O2 O12
O11 C13
C18 C17
C16
C15 C14
C19
C20
C21
C12
C5 C22
C3 C4 C1
C7 C2 C8
C10 C9 C28
C29 C30 C25 C26 C35
C34 C31 C33 C32
N6
O8 N3
N1 O9
O7 O1
Dyl O3
O10 O6 O4
O14
N2 C27
C11
O15 C36
N4
C6
C23 N5
C24
O13
FIGURE 27 Crystal structure of complex [Dy(LH)3(NO3)3]. LH is the Schiff’s base ligandL4H with CnH2nþ1¼CH3, CmH2mþ1¼C4H9. Reprinted with permission from Binnemans et al.
(2000a). Copyright 2000 American Chemical Society.
It turned out that the stoichiometry of these complexes with deprotonated Schiff’s base ligands is variable. Although the complexes prepared at room temperature have the [R(LH)3X3] stoichiometry, the complexes prepared at higher temperatures, often have the stoichiometry [R(LH)2LX2]. This can be explained by the stronger dissociation of the phenolic proton of the Schiff’s base ligand at higher temperatures. The temperature is thus a critical factor in the synthesis of these lanthanidomesogens. One should not heat the ethano- lic solution above 40C, if formation of [R(LH)3X3] complexes is wanted.
It should be noted that the proton transfer from the phenolic oxygen atom to the imine nitrogen atom in nonmesogenic Schiff’s bases has been studied in detail by both experimental and computational techniques (Filarowski et al., 2004; Koll et al., 2007).
All the lanthanide complexes of the one-ring salicylaldimine Schiff’s base ligands exhibit a smectic A phase. Neither the alkoxy chain length (Binne- mans et al., 2000a), nor theN-alkyl chain length has a substantial influence on the transition temperatures (Van Deun and Binnemans, 2000). However, the position of the alkoxy chain is of importance: a shift of the chain from the 4-position (ligand L4H. CnH2nþ1¼C8H17, CmH2mþ1¼C18H37) to the 5-position (ligand L5H) led to the disappearance of the liquid-crystalline behavior in the corresponding lanthanide complexes (Van Deun and Binne- mans, 2003). Also a chain on the phenyl ring is a requirement for liquid- crystallinity of the lanthanide complexes. Complexes of ligands without an alkoxy chain are not liquid-crystalline (Van Deun and Binnemans, 2003;
ligand L6H). Even a methoxy chain is sufficient to get LCs, provided that the N-alkyl chain has a sufficient length (ligand L4H. CnH2nþ1¼CH3, CmH2mþ1¼C18H37). For the nitrate series, the lanthanide ion has a strong influence on the mesophase behavior (Fig. 28; Binnemans et al., 1999c).
Whereas the melting point increases over the lanthanide series, the clearing point decreases simultaneously, so that the overall effect is a decrease of the mesophase stability range over the lanthanide series. The fact that there exists a correlation between the ionic radius of the lanthanide ion and the liquid- crystalline properties is convincingly demonstrated by comparison of the ther- mal properties of the holmium(III) complex (Cr 134 SmA 144 I) with those of the corresponding yttrium(III) complex (Cr 132 SmA 142 I;Binnemans et al., 1999c; Collinson et al., 2001). It is known that the ionic radii of Ho3þand Y3þ are very similar. The increase in melting points in the La-Lu series (seeFig. 28) can be attributed to a stronger electrostatic interaction between the smaller lanthanide ions and the ligands. As the size of the lanthanide ion becomes smaller over the lanthanide series (lanthanide contraction), whilst the charge remains constant, the charge density of the lanthanide ion increases and therefore the electrostatic interactions with the ligands become stronger. The decrease of the clearing point over the lanthanide series is more difficult to explain, but it presumably reflects the stronger steric interactions between the ligands in the complexes with the smaller lanthanide ions. It is
also not evident why this strong dependence of the melting and clearing tem- peratures on the lanthanide ion is observed for complexes with nitrate counter ions, but not for the corresponding chloride complexes (Binnemans et al., 2002a; Van Deun and Binnemans, 2001a). For the dodecylsulfate complexes, the trend over the lanthanide series is even opposite to that observed for the nitrate complexes: decrease in melting point over the lanthanide series, and as a consequence an increase in mesophase stability over the lanthanide series (Van Deun and Binnemans, 2001b). It is evident that further work is required to give an adequate explanation for the observed relationship between the thermal and structural properties of these Schiff’s base metallo- mesogens. Counter ions other than the nitrate group have been investigated, but much less is known about their structural features, except that probably always zwitterionic Schiff’s base ligands are present. It has already been men- tioned that the chloride complexes have higher transition temperatures than the corresponding nitrate complexes. Because chloride ions can only be monodentate ligands and because the lanthanide ions prefer high coordination numbers (typically 8 or 9), complexes of the type [R(LH)3Cl3] are most likely dimeric or even oligomeric. In contrast to the nitrate complexes, the lantha- nide ion has a much less pronounced influence on the transition temperatures of the chloride complexes: both melting and clearing points remain virtually constant over the lanthanide series. InTables 4 and 5, the transition tempera- tures of the Schiff’s base complexes with nitrate and chloride anions, respectively, are summarized
80 90 100 110 120 130 140 150 160
Ce Pm
Cr
I
SmA
Tm Er Ho Dy Tb Gd Eu Sm
Nd Yb Lu
Pr La
Temperature (°C)
FIGURE 28 Influence of the lanthanide ion on the transition temperatures of the complexes [R (LH)3(NO3)3]. LH is the Schiff’s base ligandL4Hwith CnH2nþ1¼C8H17and CmH2mþ1¼C18H37. Cr, crystalline phase; SmA, smectic A phase; I, isotropic liquid. (Drawn using the data inTable 1 ofBinnemans et al., 1999c).
TABLE 4 Thermal Behavior of the Lanthanide Complexes of the One-Ring Schiff’s Base Ligands L4H with Nitrate Counter Ions
Compound CnH2nþ1 CmH2mþ1 Temperatures (C) Reference [Nd(LH)3(NO3)3] CH3 C18H37 Cr 119 SmA 127 A Binnemans et al.
(2000a) [Nd(LH)3(NO3)3] C2H5 C18H37 Cr 132 SmA 147 A Binnemans et al.
(2000a) [Nd(LH)3(NO3)3] C3H7 C18H37 Cr 112 SmA 149 A Binnemans et al.
(2000a) [Nd(LH)3(NO3)3] C4H9 C18H37 Cr 119 SmA 158 A Binnemans et al.
(2000a) [Nd(LH)3(NO3)3] C5H11 C18H37 Cr 115 SmA 155 A Binnemans et al.
(2000a) [Nd(LH)3(NO3)3] C6H13 C18H37 Cr 110 SmA 156 A Binnemans et al.
(2000a) [Nd(LH)3(NO3)3] C7H15 C18H37 Cr 104 SmA 155 A Binnemans et al.
(2000a) [Tb(LH)2L(NO3)2] C7H15 C14H29 Cr 141 (SmA 139) I Galyametdinov
et al. (1996a) [Dy(LH)2L(NO3)2] C7H15 C14H29 Cr 143 (SmA 142) Ia Galyametdinov
et al. (1996a) [La(LH)2L(NO3)2] C7H15 C16H33 Cr 92 SmX 128 I Ovchinnikov et al.
(1995)
[Gd(LH)2L(NO3)2] C7H15 C16H33 Cr 128 SmA 146 I Ovchinnikov et al.
(1995)
[Dy(LH)2L(NO3)2] C7H15 C16H33 Cr 140 SmA 142 I Ovchinnikov et al.
(1995) [La(LH)2L(NO3)2] C7H15 C18H37 Cr 146 (SmA 145) Ia Galyametdinov
et al. (1994a) Cr 127 SmA 165 I Galyametdinov
et al. (1996b) [Nd(LH)2L(NO3)2] C7H15 C18H37 Cr 135 SmA 146 I Galyametdinov
et al. (1996b) [Eu(LH)2L(NO3)2] C7H15 C18H37 Cr 140 SmA 153 I Galyametdinov
et al. (1996b) [Gd(LH)2L(NO3)2] C7H15 C18H37 Cr 135 SmA 146 I Galyametdinov
et al. (1994a) Cr 148 SmA 155 I Galyametdinov
et al. (1996b) Continued
TABLE 4 Thermal Behavior of the Lanthanide Complexes of the One-Ring Schiff’s Base Ligands L4H with Nitrate Counter Ions—Cont’d
Compound CnH2nþ1 CmH2mþ1 Temperatures (C) Reference [Tb(LH)2L(NO3)2] C7H15 C18H37 Cr 148 SmA 151 I Galyametdinov
et al. (1996b) [Dy(LH)2L(NO3)2] C7H15 C18H37 Cr 138 SmA 141 I Galyametdinov
et al. (1994a) Cr 151 (SmA 150) Ia Galyametdinov
et al. (1996b) [Y(LH)3(NO3)3] C8H17 C18H37 Cr 132 SmA 141 I Binnemans et al.
(1999c) [La(LH)3(NO3)3] C8H17 C18H37 Cr 83 SmA 165 I Binnemans et al.
(1999c) [Pr(LH)3(NO3)3] C8H17 C18H37 Cr 90 Sm 163 I Binnemans et al.
(1999c) [Nd(LH)3(NO3)3] C8H17 C18H37 Cr 95 SmA 159 I Binnemans et al.
(1999c, 2000a) [Sm(LH)3(NO3)3] C8H17 C18H37 Cr 105 SmA 154 I Binnemans et al.
(1999c) [Eu(LH)3(NO3)3] C8H17 C18H37 Cr 108 SmA 151 I Binnemans et al.
(1999c) [Gd(LH)3(NO3)3] C8H17 C18H37 Cr 121 SmA 150 I Binnemans et al.
(1999c) [Tb(LH)3(NO3)3] C8H17 C18H37 Cr 128 SmA 148 I Binnemans et al.
(1999c) [Dy(LH)3(NO3)3] C8H17 C18H37 Cr 131 SmA 146 I Binnemans et al.
(1999c) [Ho(LH)3(NO3)3] C8H17 C18H37 Cr 134 SmA 144 I Binnemans et al.
(1999c) [Er(LH)3(NO3)3] C8H17 C18H37 Cr 135 SmA 142 I Binnemans et al.
(1999c) [Tm(LH)3(NO3)3] C8H17 C18H37 Cr 139 SmA 142 I Binnemans et al.
(1999c) [Yb(LH)3(NO3)3] C8H17 C18H37 Cr 138 SmA 141 I Binnemans et al.
(1999c) [Lu(LH)3(NO3)3] C8H17 C18H37 Cr 135 SmA 139 I Binnemans et al.
(1999c) [Nd(LH)3(NO3)3] C9H21 C18H37 Cr 100 SmA 158 I Binnemans et al.
(2000a)
TABLE 4 Thermal Behavior of the Lanthanide Complexes of the One-Ring Schiff’s Base Ligands L4H with Nitrate Counter Ions—Cont’d
Compound CnH2nþ1 CmH2mþ1 Temperatures (C) Reference [Nd(LH)3(NO3)3] C10H21 C18H37 Cr 101 SmA 158 I Binnemans et al.
(2000a) [Nd(LH)3(NO3)3] C11H23 C18H37 Cr 103 SmA 157 I Binnemans et al.
(2000a) [Pr(LH)3(NO3)3] C12H25 C16H33 Cr 105 SmA 148 I Binnemans et al.
(2000a) [Nd(LH)3(NO3)3] C12H25 C16H33 Cr 105 SmA 147 I Binnemans et al.
(2000a) [Gd(LH)3(NO3)3] C12H25 C16H33 Cr 107 SmA 145 I Binnemans et al.
(2000a) [Tb(LH)3(NO3)3] C12H25 C16H33 Cr 107 SmA 147 I Binnemans et al.
(2000a) [Er(LH)3(NO3)3] C12H25 C16H33 Cr 107 SmA 147 I Binnemans et al.
(2000a) [La(LH)2L(NO3)2] C12H25 C18H37 Cr 81 SmA 138 I Galyametdinov
et al. (1996a) [La(LH)3(NO3)3] C12H25 C18H37 Cr 81 SmA 138 I Binnemans et al.
(2000a) [Nd(LH)2L(NO3)2] C12H25 C18H37 Cr 100 SmA 151 I Galyametdinov
et al. (1996a) [Nd(LH)3(NO3)3] C12H25 C18H37 Cr 100 SmA 158 I Binnemans et al.
(2000a) [Eu(LH)2L(NO3)2] C12H25 C18H37 Cr 113 SmA 147 I Galyametdinov
et al. (1996a) [Gd(LH)2L(NO3)2] C12H25 C18H37 Cr 115 SmA 147 I Galyametdinov
et al. (1995) C12H25 C18H37 Cr 112 SmA 144 I Galyametdinov
et al. (1996a) [Tb(LH)2L(NO3)2] C12H25 C18H37 Cr 114 SmA 148 I Galyametdinov
et al. (1996a) Cr 114 SmA 147 I Galyametdinov
et al. (1995) Cr 96 SmA 148 I Galyametdinov
et al. (1999) [Dy(LH)2L(NO3)2] C12H25 C18H37 Cr 130 SmA 144 I Galyametdinov
et al. (1996a) Continued