Water-soluble gadofullerenes: toward high-relaxivity, pH-responsive MRI contrast agents

The water-soluble endohedral gadofullerene derivatives, Gd@C(60)(OH)(x) and Gd@C(60)[C(COOH)(2)](10), have been characterized with regard to their MRI contrast agent properties. Water-proton relaxivities have been measured in aqueous solution at variable temperature (278-335 K), and for the first time for gadofullerenes, relaxivities as a function of magnetic field (5 x 10(-4) to 9.4 T; NMRD profiles) are also reported. Both compounds show relaxivity maxima at high magnetic fields (30-60 MHz) with a maximum relaxivity of 10.4 mM(-1) s(-1) for Gd@C(60)[C(COOH)(2)](10) and 38.5 mM(-1) s(-1) for Gd@C(60)(OH)(x) at 299 K. Variable-temperature, transverse and longitudinal (17)O relaxation rates, and chemical shifts have been measured at three magnetic fields (B = 1.41, 4.7, and 9.4 T), and the results point exclusively to an outer sphere relaxation mechanism. The NMRD profiles have been analyzed in terms of slow rotational motion with a long rotational correlation time calculated to be tau(R)(298) = 2.6 ns. The proton exchange rate obtained for Gd@C(60)[C(COOH)(2)](10) is k(ex)(298) = 1.4 x 10(7) s(-1) which is consistent with the exchange rate previously determined for malonic acid. The proton relaxivities for both gadofullerene derivatives increase strongly with decreasing pH (pH: 3-12). This behavior results from a pH-dependent aggregation of Gd@C(60)(OH)(x) and Gd@C(60)[C(COOH)(2)](10), which has been characterized by dynamic light scattering measurements. The pH dependency of the proton relaxivities makes these gadofullerene derivatives prime candidates for pH-responsive MRI contrast agent applications.     

水溶性金属勒烯衍生物的合成和表征

金属富勒烯具有表面积大(2 nm2)、整体电中性、金属离子的解离常数Kd为0等独特的性质, 在医学上具有重要的应用价值[1～7]. 要将其用于生物体系, 需引入亲水基团. 水溶性Gd@C82(OH)x已被证实是一种比临床上应用的GdDTPA更好的核磁成像造影剂(其弛豫率比GdDTPA高20倍[7]), 并有望用作放射性示踪剂和放射性药物等, 且在生物体内外具有稳定性[2～6], 是生物医学上很有吸引力的材料. 本文在高效合成、分离纯化 Gd@C82的基础上合成了其多羟基衍生物、多取代氨基酸衍生物和多取代氨基磺酸衍生物, 并作了初步分析.     

Where does the metal cation stay in Gd@C2v(9)-C82? A single-crystal X-ray diffraction study

Metal positions in endohedral metallofullerenes (EMFs) are of special importance because their molecular symmetry and intrinsic properties are strongly influenced by the location and motion of the encapsulated metals. X-ray analyses of the cocrystals of Gd@C(2v)(9)-C(82) with nickel(II) octaethylporphyrin [Ni(II)(OEP)] reveal that the Gd(3+) cation is off-center, being located under a hexagonal ring along the 2-fold axis of the C(2v)(9)-C(82) cage. This result is in sharp contrast to that of a previous study, showing that Gd@C(2v)(9)-C(82) has an anomalous endohedral structure, with the metal being positioned over a [6,6] bond, which is opposite to the hexagonal ring along the C(2) axis (Phys. Rev. B 2004, 69, 113412). In agreement with theoretical calculations and related studies, it is conclusive that the single rare-earth metal in M@C(2v)(9)-C(82) always tends to coordinate with the hexagonal ring along the 2-fold axis, instead of interacting with the [6,6] bond on the other end, regardless of the type of metal atom.     

金属富勒烯的质谱研究

利用电弧放电法合成笼内金属富勒烯Gd@C₈₂,Gd₂@C₈₀,Gd@C₈₀实验结果表明,两步高温高压法(1,2,4-三甲基苯,吡啶)可有效地提取金属富勒烯Gd@C₈₂.本文分别利用ESI-MS,REC-MS,MALDI-TOF-MS质谱技术研究了Gd@C₈₂,Gd₂@C₈₀,Gd@C₈₀和富勒烯Cn(n=60,70,82,84…)的气相负离子特性.结果表明,包入Gd³⁺后非极性的C₈₂转变为极性的Gd@C₈₂分子;金属离子Gd³⁺处于C₈₂^3-笼中非中心的位置.     

Iron Sulfido Derivatives of the Fullerenes C(60) and C(70)

Toluene solutions of C(60) react upon UV irradiation with Fe(2)S(2)(CO)(6) to give C(60)[S(2)Fe(2)(CO)(6)](n)() where n = 1-6. C(60)[S(2)Fe(2)(CO)(6)](n)() where n = 1-3 have been isolated and characterized. Crystallographic studies of C(60)S(2)Fe(2)(CO)(6) show that the S-S bond of the Fe(2) reagent is cleaved to give a dithiolate with idealized C(2)(v)() symmetry. The addition occurred at a 6,6 fusion, and the metrical details show that the Fe(2) portion of the molecule resembles C(2)H(4)S(2)Fe(2)(CO)(6). IR spectroscopic measurements indicate that the Fe(2)(CO)(6) subunits in the multiple-addition species (n > 1) interact only weakly. UV-vis spectra of the adducts show a shift to shorter wavelength with addition of each S(2)Fe(2)(CO)(6) unit. Photoaddition of the phosphine complex Fe(2)S(2)(CO)(5)(PPh(3)) to C(60) gave C(60)[S(2)Fe(2)(CO)(5)(PPh(3))](n)(), where n = 1-3. (31)P{(1)H} NMR studies show that the double adduct consists of multiple isomers. Photoaddition of Fe(2)S(2)(CO)(6) to C(70) gave a series of adducts C(70)[S(2)Fe(2)(CO)(6)](n)() where n = 1-4. HPLC analyses show one, four, and three isomers for the adducts, respectively.     

Lanthanoid endohedral metallofullerenols for MRI contrast agents

Water-soluble multi-hydroxyl lanthanoid (La, Ce, Gd, Dy, and Er) endohedral metallofullerenes (metallofullerenols, M@C(82)(OH)(n)()) have been synthesized and characterized for the use of magnetic resonance imaging (MRI) contrast agents. The observed longitudinal and transverse relaxivities for water protons, r(1) and r(2), of the metallofullerenols are in the range 0.8-73 and 1.2-80 (sec(-1)mM(-1)), respectively, which are significantly higher than those of the corresponding lanthanoid-DTPA chelate complexes. Among these Gd-metallofullerenols, Gd@C(82)(OH)(n)() has exhibited the highest r(1) and r(2) values in consistent with our previous results. The observed large r(1) of the current metallofullerenols can mainly be ascribed to the dipole-dipole relaxation together with a substantial decrease of the overall molecular rotational motion. The large r(2), except for the Gd-metallofullerenols, have been attributed to the so-called Curie spin relaxation. The MRI phantom studies are also performed and are consistent with these results. The metallofullerenols will be an ideal model for future MRI contrast agents with higher proton relaxivities.     

Synthesis and characterization of endohedral metallofulleride K(18-crown-6)[Ho@C82(C 2v)]

Russian Chemical Bulletin - Endohedral metallofulleride K(18-crown-6)[Ho@C82(C 2v)] was synthesized for the first time using a redox reaction of endohedral metallofullerene Ho@C82(C 2v) with the...     

The Interaction of C60, C70, and C60(CN)2 radical anions with cobalt(II) tetraphenylporphyrin in solid multicomponent complexes

A method for the synthesis of the multicomponent ionic complexes: [Cr(I)(C(6)H(6))(2) (.+)][Co(II)(tpp)(fullerene)(-)].C(6)H(4)Cl(2), comprising bis(benzene)chromium (Cr(C(6)H(6))(2)), cobalt(II) tetraphenylporphyrin (Co(II)(tpp)), fullerenes (C(60), C(60)(CN)(2), and C(70)), and o-dichlorobenzene (C(6)H(4)Cl(2)) has been developed. The monoanionic state of the fullerenes has been proved by optical absorption spectra in the UV/vis/NIR and IR ranges. The crystal structures of the ionic [[Cr(I)(C(6)H(6))(2)](.+)](1.7)[[Co(II)(tpp)(C(60))](2)](1.7-). 3.3 C(6)H(4)Cl(2) and [[Cr(I)(C(6)H(6))(2)] (.+)](2)[Co(II)(tpp)[C(60)(CN)(2)]](-)[C(60)(CN)(2) (.-)]).3 C(6)H(4)Cl(2) are presented. The essentially shortened Co.C(fullerene) bond lengths of 2.28-2.32 A in these complexes indicate the formation of sigma-bonded [Co(II)(tpp)][fullerene](-) anions, which are diamagnetic. All the ionic complexes are semiconductors with room temperature conductivity of 2 x 10(-3)-4 x 10(-6) S cm(-1), and their magnetic susceptibilities show Curie-Weiss behavior. The neutral complexes of Co(II)(tpp) with C(60), C(60)(CN)(2), C(70), and Cr(0)(C(6)H(6))(2), as well as the crystal structures of [Co(II)(tpp)](C(60)).2.5 C(6)H(4)Cl(2), [Co(II)(tpp)](C(70)). 1.3 CHCl(3).0.2 C(6)H(6), and [Cr(0)(C(6)H(6))(2)][Co(II)(tpp)] are discussed. In contrast to the ionic complexes, the neutral ones have essentially longer Co.C(fullerene) bond lengths of 2.69-2.75 A.     

Arbuzov chemistry with chlorofullerene C(60)Cl(6): a powerful method for selective synthesis of highly functionalized [60]fullerene derivatives

We report Arbuzov-type reactions of chlorofullerene C(60)Cl(6) with trialkyl phosphites producing highly functionalized fullerene derivatives C(60)[P(O)(OR)(2)](5)H with high yields. The designed family of [60]fullerene phosphonic acids and their esters showed unusual properties which might find valuable material science applications.     

Gd@ C2n的高效合成与提取

Endohedral metallofullerene Gd@C2n were synthesized with high-yield using the carbon-arc discharge method of activating the Gd2O3-containing graphite anode in situ and back-burning technique. A series of Cd@C(2n) for 2n from 70 to 96 were effectively extracted by toluene at high-temperature and under high-pressure condition. Gd@C(82), Gd@C(74) were considered to be fairly stable and soluble metallofullerene species.     

Probing the role of encapsulated alkaline earth metal atoms in endohedral metallofullerenes M@C76 (M = Ca, Sr, and Ba) by first-principles calculations

By means of density functional theory and statistical mechanics, we investigate the geometric and electronic structures, thermodynamic stability and infrared (IR) vibrational frequencies of alkaline earth metal endohedral fullerenes, M@C(76) (M = Ca, Sr, and Ba). The results reveal that M@C(1)(17,459)-C(76) possesses the lowest energy followed by M@C(2v)(19,138)-C(76) with a very small energy difference. Both the structures have a pair of adjacent pentagons and are related by a single Stone-Wales transformation. Equilibrium statistical thermodynamic analyses based on Gibbs energy treatments suggest that M@C(1)(17,459)-C(76) has a prominent thermodynamic stability at higher temperatures, in contrast with M@C(2v)(19,138)-C(76) whose thermodynamic stability is affected by the encapsulated metal atom. The encapsulated metallic atoms as well as cage structures significantly influence the electronic properties of endohedral fullerenes such as electron affinities and ionization potentials. On the other hand, the singlet-triplet splitting energy ΔE(S-T) depends on the cage structures. In addition, IR spectra and chemical shifts of these compounds have been computed to assist further experimental characterization.     

Chemical oxidation of endohedral metallofullerenes: identification and separation of distinct classes

Chemical oxidation is useful for solubilizing and separating endohedral metallofullerenes, as demonstrated here by a separation of three categories of Gd@C2n species and by the solubilization of Tm@C60+ and Tm@C70+ for the first time.     

Ti2C80 is more likely a titanium carbide endohedral metallofullerene (Ti2C2)@C78

We show by means of density functional calculations that the previously synthesized metallofullerene Ti2C80 does not take the form of Ti2@C80, but is a titanium carbide endohedral metallofullerene, Ti2C2@C78, that has a C78(6-)(D3h) cage which follows faithfully the stable closed-shell electronic rule.     

Separation of N2@C60 and N@C60

We describe the HPLC separation and identification of N@C60 and N2@C60. These species were observed after eleven sequential HPLC separations. Their retention times are in the same range as those of the other noninteractive endohedral species of C60, such as noble gas endohedral C60. The separation factors of these endohedrals were evaluated by using a mixture of hexane/toluene as eluent. We note that this is the first evidence for the N2@C60 molecule existing in the form of endohedral C60 complex.     

Supramolecular structural variations with changes in anion and solvent in silver(I) complexes of a semirigid, bitopic tris(pyrazolyl)methane ligand

The bitopic ligand p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2) (pz = pyrazolyl ring) that contains two tris(pyrazolyl)methane units connected by a semirigid organic spacer reacts with silver(I) salts to yield [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgX)(2)]( infinity ), where X = CF(3)SO(3)(-) (1), SbF(6)(-) (2), PF(6)(-) (3), BF(4)(-) (4), and NO(3)(-) (5). Crystallization of the first three compounds from acetone yields [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgCF(3)SO(3))(2)]( infinity ) (1a), [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgSbF(6))(2)[(CH(3))(2)CO](2)]( infinity ) (2b), and [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)AgPF(6)]( infinity ) (3a), where the stoichiometry for the latter compound has changed from a metal:ligand ratio of 2:1 to 1:1. The structure of 1a is based on helical argentachains constructed by a kappa(2)-kappa(1) coordination to silver of the tris(pyrazolyl)methane units. These chains are organized into a tubular 3D structure by cylindrical [(CF(3)SO(3))(6)](6)(-) clusters that form weak C-H...O hydrogen bonds with the bitopic ligand. The same kappa(2)-kappa(1) coordination is present in the structure of 2a, but the structure is organized by six different tris(pyrazolyl)methane units from six ligands bonding with six silvers to form a 36-member argentamacrocycle core. The cores are organized in a tubular array by the organic spacers where each pair of macrocycles sandwich six acetone molecules and one SbF(6)(-) counterion. The structure of 3a is based on a kappa(2)-kappa(0) coordination mode of each tris(pyrazolyl)methane unit forming a helical coordination polymer, with two strands organized in a double stranded helical structure by a series of C-H...pi interactions between the central arene rings. Crystallization of 2-4 from acetonitrile yields complexes of the formula [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)[(AgX)(2)(CH(3)CN)(n)]]( infinity ) where n = 2 for X = SbF(6)(-) (2b), X = PF(6)(-) (3b) and n = 1 for X = BF(4)(-) (4b). All three structures contain argentachains formed by a kappa(2)-kappa(1) coordination mode of the tris(pyrazolyl)methane units linked by the organic spacer and arranged in a 2D sheet structure with the anions sandwiched between the sheets. Crystallization of 5 from acetonitrile yields crystals of the formula [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgNO(3))(2)(CH(3)CN)(4)]( infinity ), where the nitrate is bonded to the silver. The argentachains, again formed by kappa(2)-kappa(1) coordination, are arranged in W-shaped sheets that have an overall configuration very different from 2b-4b. Treating [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgSbF(6))(2)]( infinity ) with a saturated aqueous solution of KPF(6) or KO(3)SCF(3) slowly leads to complete exchange of the anion. Crystallization of a sample that contains an approximately equal mixture of SbF(6)(-)/PF(6)(-) from acetonitrile yields [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)[Ag(2)(PF(6))(0.78(1))(SbF(6))(1.22(1))(CH(3)CN)(2)][(CH(3)CN)(0.25) (C(4)H(10)O)(0.25)]]( infinity ), a compound with a sheet structure analogous to 2b-4b. Crystallization of the same mixture from acetone yields [p-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)(AgSbF(6))[(CH(3))(2)CO](1.5)]( infinity ), where the metal-to-ligand ratio is 1:1 and the [C(pz)(3)] units are kappa(2)-kappa(0) bonded forming a coordination polymer. The supramolecular structures of all species are organized by a combination of C-H...pi, pi-pi, or weak C-H-F(O) hydrogen bonding interactions.     

Coordination chemistry of the soluble metal oxide analogue [Mo5O13(OCH3)4(NO)]3- with manganese carbonyl species

The reactions of neutral or cationic manganese carbonyl species towards the oxo-nitrosyl complex [Na(MeOH)[Mo(5)O(13)(OCH(3))(4)(NO)]](2-) have been investigated in various conditions. This system provides an unique opportunity for probing the basic reactions involved in the preparation of solid oxide-supported heterogeneous catalysts, that is, mobility of transition-metal species at the surface and dissolution-precipitation of the support. Under nitrogen and in the dark, the reaction of in situ generated fac-[Mn(CO)(3)](+) species with (nBu(4)N)(2)[Na(MeOH)-[Mo(5)O(13)(OMe)(4)(NO)]] in MeOH yields (nBu(4)N)(2)[Mn(CO)(3)(H(2)O)[Mo(5)O(13)(OMe)(4)(NO)]] at room temperature, while (nBu(4)N)(3)[Na[Mo(5)O(13)(OMe)(4)(NO)](2)[Mn(CO)(3)](2)] is obtained under reflux. The former transforms into the latter under reflux in methanol in the presence of sodium bromide; this involves the migration of the fac-[Mn(CO)(3)](+) moiety from a basal kappa(2)O coordination site to a lateral kappa(3)O site. Oxidation and decarbonylation of manganese carbonyl species as well as degradation of the oxonitrosyl starting material and reaggregation of oxo(methoxo)molybdenum fragments occur in non-deareated MeOH, and both (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(16)(OMe)(2)](2)[Mn(CO)(3)](2)] and (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(13)(OMe)(4)(NO)](2)] as well as (nBu(4)N)(2)[MnBr[Mo(5)O(13)(OMe)(4)(NO)]] have been obtained in this way. The rhenium analogue (nBu(4)N)(2)[Re(CO)(3)(H(2)O)[Mo(5)O(13)(OMe)(4)(NO)]] has also been synthesized. The crystal structures of (nBu(4)N)(2)[Re(CO)(3)(H(2)O)[Mo(5)O(13)(OMe)(4)(NO)]], (nBu(4)N)(3)[Na[Mo(5)O(13)(OMe)(4)(NO)](2)[Mn(CO)(3)](2)], (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(16)(OMe)(2)](2)[Mn(CO)(3)](2)], (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(13)(OMe)(4)(NO)](2)] and (nBu(4)N)(2)[MnBr[Mo(5)O(13)(OMe)(4)(NO)]] have been determined.     

Does Gd@C82 have an anomalous endohedral structure? Synthesis and single crystal X-ray structure of the carbene adduct

We report here the results on single crystal X-ray crystallographic analysis of the Gd@C82 carbene adduct (Gd@C82(Ad), Ad = adamantylidene). The Gd atom in Gd@C82(Ad) is located at an off-centered position near a hexagonal ring in the C2v-C82 cage, as found for M@C82 (M = Sc and La) and La@C82(Ad). Theoretical calculation also confirms the position of the Gd atom in the X-ray crystal structure.     

Synthesis and structure of the pentacopper(II) substituted tungstosilicate [Cu5(OH)4(H2O)2(A-alpha-SiW9O33)2]10-

The dimeric, pentacopper(II) substituted tungstosilicate [Cu(5)(OH)(4)(H(2)O)(2)(A-alpha-SiW(9)O(33))(2)](10-) (1) has been synthesized in good yield using a one-pot procedure by reaction of Cu(2+) ions with the trilacunary precursor salt K(10)[A-alpha-SiW(9)O(34)]. The title polyanion represents the first polyoxotungstate substituted by 5 copper centers and the central copper-hydroxo-aqua fragment is completely unprecedented. In the course of the reaction, two [A-alpha-SiW(9)O(34)](10-) Keggin half-units have fused in an asymmetrical fashion resulting in the lacunary polyoxotungstate [Si(2)W(18)O(66)](16-). The vacancy in this species is stabilized by a magnetic cluster of five octahedrally coordinated Cu(2+) ions resulting in polyanion 1 with C(2v) symmetry.     

A density functional theory study of shake-up satellites in photoemission of carbon fullerenes and nanotubes

Carbon 1s shake-up spectra of fullerenes C(60), C(70), and C(82) and single-walled carbon nanotubes (SWCNTs) of (5,5), (6,5), and (7,6) have been investigated by using equivalent core hole Kohn-Sham density functional theory approach, in which only one-electron transition between molecular orbitals within core-hole potential is considered. The calculated spectra are generally in good agreement with results of equivalent core-hole time-dependent density functional theory calculations and available experiments, and reliable assignments for the complicated shake-up spectra of such large systems are provided. Calculations have also been performed for endohedral metallofullerene Gd@C(82) to demonstrate the possible use of shake-up processes to identify the charge transfer between the metal ion and the carbon cage. It is found that the exciton binding energy of all systems under investigation is around 0.5 eV.     

Metal-centered deltahedral Zintl ions: synthesis of [Ni@Sn9]4- by direct extraction from intermetallic precursors and of the vertex-fused dimer [{Ni@Sn8(μ-Ge)(1/2)}2]4-

Ni-centered deltahedral Sn(9) clusters with a charge of 4-, i.e., [Ni@Sn(9)](4-), were extracted in ethylenediamine in high yield directly from intermetallic precursors with the nominal composition "K(4)Sn(9)Ni(3)". The new endohedral clusters were crystallized and structurally characterized in K[K(18-crown-6)](3)[Ni@Sn(9)]·3benzene (1a, triclinic, P1?, a = 10.2754(5) ?, b = 19.5442(9) ?, and c = 20.5576(13) ?, α = 73.927(3)°, β = 79.838(4)°, and γ = 84.389(3)°, V = 3899.6(4) ?(3), Z = 2) and K[K(2,2,2-crypt)](3)[Ni@Sn(9)] (1b, triclinic, P1, a = 15.8028(8) ?, b = 16.21350(9) ?, and c = 20.1760(12) ?, α = 98.71040(10)°, β = 104.4690(10)°, and γ = 118.3890(10)°, V = 4181.5(4) ?(3), Z = 2). The alternative method of a post-synthetic insertion of a Ni atom in empty Sn(9) clusters by a reaction with Ni(cod)(2) predominantly produces the more-oxidized clusters with a charge of 3-, i.e., the recently reported [Ni@Sn(9)](3-). Nonetheless, using substoichiometric amounts of 18-crown-6 as a cation sequestering agent, we also have been able to isolate the 4- clusters as a minor phase from such reactions. They were structurally characterized in K[K(en)][K(18-crown-6)](2)[Ni@Sn(9)]·0.5en (2, monoclinic, P2(1)/n, a = 10.4153(5) ?, b = 25.6788(11) ?, and c = 20.6630(9) ?, β = 102.530(2)°, V = 5394.7(4) ?(3), Z = 2). The ability of the Ni-centered clusters to exist with both 3- and 4- charges parallels the same ability of the empty clusters and is very promising for similarly rich chemistry involving electron transfer and flexible "oxidation states". We also report the synthesis and characterization of the endohedral heteroatomic dimer [{Ni@Sn(8)(μ-Ge)(1/2)}(2)](4-) composed of two [Ni@(Sn(8)Ge)]-clusters fused at the Ge-vertex. The dimer was synthesized by reacting an ethylenediamine solution of a ternary precursor with the nominal composition "K(4)Ge(4.5)Sn(4.5)", which is known to produce heteroatomic Ge(9-x)Sn(x) clusters, with Ni(cod)(2). It is isostructural with the reported [{Ni@Sn(8)(μ-Sn)(1/2)}(2)](4-) and is structurally characterized in [K-(2,2,2-crypt)](4)[{Ni@Sn(8)(μ-Ge)(1/2)}(2)]·2en (3, monoclinic, C2/c, a = 30.636(2) ?, b = 16.5548(12) ?, and c = 28.872(2) ?, β = 121.2140(10)°, V = 12523.5(15) ?(3), Z = 4).