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Multiple-Decker Metal Porphyrins
Published in Toshio Naito, Functional Materials, 2019
The first synthesis of a sandwich-type tetrapyrrole metal complex, in 1936 by Linstead and coworkers, produced bis(phthalocyanine)-Sn(VI) instead of por (Fig. 6.2) [2]. Phthalocyanines are also macrocyclic molecules and have four inward nitrogen atoms. The double-decker structure of Sn(Pc)2, where Pc is phthalocyanine, was proven by X-ray crystallographic analysis in 1973 (Fig. 6.3). [3]. The metal center is surrounded by the eight nitrogen atoms in a square antiprism geometry. The macrocyclic systems are rotated 42° with respect to one another, and the two square planes composed of coordinated four nitrogens are 2.70 Å apart.
Eu3+-Based Orange-Red-Emitting Inorganic Color Convertors: An Overview
Published in Sanjay J. Dhoble, B. Deva Prasad Raju, Vijay Singh, Phosphors Synthesis and Applications, 2018
The structure of AgGd(WO4)2 is shown in Fig. 8.9 a. In this structure, the Gd3+ ion is eight-coordinated by oxygen atoms, forming a square antiprism. The polyhedra form a single chain by edge sharing. The Ag+ ion is twelve-coordinated by oxygen atoms, forming a distorted icosahedron. By edge sharing, these polyhedra form a bidimensional layer consisting of chains. Hexavalent tungsten (W6+) is located in a distorted octahedron with three shorter W-O distances ranging from 1.747 to 2.359 A. In this structure, all the polyhedra are strongly linked by edge and corner sharing, forming a chain. GdO8 and AgO12 polyhedra are shown in Fig. 8.9 b.
Macrocyclic Receptors for Biologically Relevant Metal Ions
Published in Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney, Macrocyclic Receptors for Environmental and Biosensing Applications, 2022
Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney
The MRI contrast agent [Gd (OH2) (DTPA)]2− (Magnevist®) and Gd (DOTA)− (Dotarem®) were the first complexes approved for clinical practice and used as gold standards. The dianionic [Gd (OH2)(DTPA)]2− contains acyclic ligand DTPA, an amino polycarboxylic acid (IUPAC name: 2-[Bis[2-[bis(carboxymethyl)amino] ethyl] amino]acetic acid). It forms a stable octa-coordinated chelate as distorted TTP and the ninth coordination site was occupied by a water molecule (Caravan et al. 1999). Gd (DOTA) − (Dotarem®) also forms a very stable lanthanide chelates with macrocyclic ring structure of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid). This ligand consists of the macrocycle cyclen, which is N-functionalized with four acetic acid pendant arms and is octadentate with four nitrogen and four oxygen donor atoms as shown in Fig. 8.9. The solid-state X-ray structure of Gd (DOTA))− indicates that the Gd3+ is situated in the center of a CASP cage, with the water molecule in an axial position. These complexes are hydrophilic and in solution, they exist as stereoisomeric interchangeable molecules with a Commercially approved T1 contrast agents containing linear and cyclic ligand (Reprinted with permission of ACS (Wahsner et al. 2019).different structure (square antiprism = SA and twisted square antiprism = TSA) as shown in Fig. 8.10. High complex stability is required for good contrast images and stability constant for [Gd(OH2)(DOTA)]− ranges from 24.0 to 27.0 as reported in the literature (Clough et al. 2019). The minor isomer (TSA) exhibits faster water exchange than the major isomer (SA), suggesting that CA should adopt the TSA structure.
Dissimilarity measure of local structure in inorganic crystals using Wasserstein distance to search for novel phosphors
Published in Science and Technology of Advanced Materials, 2021
Shota Takemura, Takashi Takeda, Takayuki Nakanishi, Yukinori Koyama, Hidekazu Ikeno, Naoto Hirosaki
In this approach, W can be calculated as the local structures with different coordination numbers because the local structures are expressed as the distance distribution. To calculate W of the local structures with the different coordination numbers, seven kinds of ideal structures were selected: tetrahedron, trigonal bipyramid, octahedron, pentagonal bipyramid, cubic, square antiprism, and cuboctahedron. The center-ligand distances are the same in each ideal structure. Table 1 shows W of the seven kinds of ideal structures. The W between pentagonal bipyramid and square antiprism is the smallest at 0.067, but pentagonal bipyramid and square antiprism are dissimilar because the value is larger than 0.047 in Figure 2. Local structures with different coordination numbers indicate dissimilarity. Therefore, this quantitative dissimilarity can be calculated for any local structure, and a local structure with a different coordination number is dissimilar spontaneously.
Seven- and eight-coordinate lanthanide(III) amidophosphate complexes: synthesis, characterization and photoluminescence
Published in Journal of Coordination Chemistry, 2021
Marco Bortoluzzi, Andrea Di Vera, Luca Pietrobon, Jesús Castro
Despite all attempts, we were unable to obtain crystallized samples of [Eu(tta)3{O = P(OPh)2(NMe2)}2] and [Tb(acac)3{O = P(OPh)2(NMe2)}2] suitable for single-crystal X-ray diffraction. DFT calculations are however in agreement with the formation of eight-coordinate species when O = P(OPh)2(NMe2) is reacted with Ln(III) ions in combination with β-diketonates with relatively low steric bulk, such as tta and acac. The optimized geometries of [Eu(tta)3{O = P(OPh)2(NMe2)}2] and [Tb(acac)3{O = P(OPh)2(NMe2)}2], depicted in Figure 4, suggest that two amidophosphate ligands can coordinate the Ln(III) centers without particular elongations of the Ln-O distances. The predicted geometry of the coordination sphere, obtained on the basis of Continuous Shape Measures (CSM) calculations [66], is the square antiprism for both the compounds.
Investigation of intermolecular interactions between [Ho(H2O)8]4+ based 3D metal-organic supramolecular host and bipyridyl guest through crystal structure and Hirshfeld surface analysis
Published in Journal of Coordination Chemistry, 2021
Maxcimilan Patra, Soumen Kumar Dubey, Soumen Singha, Corrado Rizzoli, Subham Bhattacharjee, Rajat Saha
SCXRD analysis reveals that 1 is a mononuclear complex and crystallizes in the tetragonal space group I4cm. The crystallographic parameters are given in Table 1. The asymmetric unit contains one Ho4+ metal ion with 0.25 occupancy, one-half unit of TBTA moiety and one-half unit of bipy (Figure S1). The metal ion Ho14+ shows an eight coordinated distorted square antiprism geometry. Eight water molecules are coordinated with the metal ion. Ho1-Owater bond distances are 2.33(2) Å (Ho1-O1W) and 2.380(19) Å (Ho1-O2W). The coordination bond angles vary within the range of 72.5°–148.7° (Table S1). For the TBTA anion, the carboxylate groups are almost perpendicular (89.05°) to the phenyl ring. The C-O bond distances are 1.25 Å (C4-O1) and 1.22 Å (C4-O2) for the doubly deprotonated TBTA anion. For the bipyridyl molecule, both the pyridyl groups are in a plane.