SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF LANTHANIDE(III) TEXAPHYRINS

The synthesis and characterizations of several lanthanide(III) texaphy rin complexes of ,5,7,9,11(27),-12,14,16,18,20,22(25),23-tridecaene (2 ), ,9,11(27),12,14(19),15,17,20,22(25),-23-tridecaene (21), and ,5,7,9 ,11(27),12,14,16,18,20,22(25),23-tri-decaene (30), respectively, are r eported. Single crystals suitable for X-ray diffraction were obtained for the La(III) complex 3, the Gd(III) complexes 9 and 37, the Eu(III) complex 36, and the Lu(III) complex 22, by dissolving the respective complex in MeOH/CHCl3 and layering with diethyl ether. The five lantha nide(III) texaphyrin complexes all crystallize in the triclinic space group, P1BAR (No. 2), with Z = 2. The final R's, for data collected at reduced temperatures (less-than-or-equal-to 90-degrees-C), were 0.041 2 for 3, 0.0373 for 9, 0.0293 for 22, 0.0320 for 36, and 0.0477 for 37 . The complexes are characterized by five-coordination from the texaph yrin, a coordinated methanol molecule on one side and at least one sym metrically bidentate NO3- ion opposite the methanol. The 10-coordinate La(III) complex 3 has two bidentate NO3- ions on the same side of the macrocycle. The europium(III) and gadolinium(III) texaphyrins 36 and 37 are structurally isomorphous and are 9-coordinate species with a bi dentate NO3- ion and a methanol molecule on the top side of the macroc ycle. On the other hand, the lutetium(III) texaphyrin is 8-coordinate with only a single bidentate NO3-ion chelated to the ''top' side of co mplex. In an unusual case of disorder, the gadolinium-(III) texaphyrin 9 has both 9- and 1 0-coordinate species present in the solid state. The geometry of the 9-coordinate species is much like that found in 36 and 37, while the 10-coordinate Gd(III) species is similar to the La( III) species 3. Together, these structures reflect both the decrease i n coordination number and the intrinsic contraction in cation size obs erved as the lanthanide series is transversed. For instance, an averag e decrease in nitrogen-to-metal bond length of 0. 1 2 angstrom is foun d when comparing the 10-coordinate La(III) complex 3 to the 9-coordina te gadolinium(III) texaphyrin species 37 and a decrease of 0.075 angst rom is observed when comparing this latter Gd(III) complex to the 8-co ordinate Lu(III) system 22. Similarly, the 10-coordinate La(III) cente r in 3 is found to be 0.91 angstrom from the mean plane through the ri ve nitrogen donors of the macrocycle while the 8-coordinate Lu(III) ce nter in 22 is only 0.27 angstrom from the plane. Finally, the root-mea n-square deviation from planarity for the atoms of the macrocycle core is 0.15 angstrom in 3 and only 0.072 angstrom in 22, as compared to 0 .097, 0.122, and 0.120 angstrom in 9, 36, and 37, respectively.