Syntheses, Crystal Structures and Thermal Behavior of Five New Complexes Containing 2, 4, 6‐Trifluorobenzoate as Ligand

Abstract

Five new complexes containing 2, 4, 6‐trifluorobenzoateas ligand have been synthesized and structurally characterized, namely Li(C6F3H2COO)(H2O) (P21, Z = 2, 1),Cs(C6F3H2COO)(C6F3H2COOH) (P21/c, Z = 4, 2),Cu(C6F3H2COO)2(H2O)2 (P$\bar{1}$, Z = 1, 3), Cu(C6F3H2COO)2(MeOH) (P21/c. Z = 4, 4) and Ag(C6F3H2COO)(H2O) (C2/c, Z = 8, 5). 1–3 and 5 are coordination polymers forming strands (1, 3, 5) or corrugated layers (2). In 1 and 2 the benzoate ligand acts as a bridging ligand, whereas in 3 and 5 the benzoate ligand is not bridging and the molecular units are interconnected by bridging water molecules. In 4 and 5, dimeric Cu2 and Ag2 units, respectively, are formed with short M···M contacts. The dimeric units in 4 resemble the well‐known paddlewheel structural motif. In 5 these dimeric units are further connected by bridging water molecules, whereas in 4 only very weak F···H interactions connect the dimeric units. DTA/TG experiments on 1, 3 and 4 reveal that in a first step solvent molecules (H2O, MeOH) are unquestionably released. In 1–5 the torsion angles of the carboxylate group with respect to the aromatic ring deviate significantly from zero. These results are in very good agreement with the results of quantum chemical calculations of free 2, 4, 6‐trifluorobenzoic acid and its dimer at the DFT and RI‐MP2 level of theory.

Two New Coordination Polymers with UO22+ Units and Fluorinated Aromatic Carboxylate Linkers

“…These torsion angles are surprising, as the occupancy of F2 was refined to a higher value (65 %) than that of F3 (35 %). Nevertheless, a higher torsion angle is observed with F3 in α position, which is different to most reports in the literature , . In our former work with the monofluorinated 4‐ mF ‐BPTC 4– linker we found a torsion angle of 28.9(9)°, which is significantly larger than those found for anion A in this work.…”

“…Several years ago we started to synthesize fluorinated aromatic carboxylic acids,, which – in a next step – were used to synthesize new CPs and MOFs with these linkers . With respect to their structural chemistry it is a remarkable feature that the torsion angle between the phenyl ring and the carboxylate group is no longer close to 0° as found in most MOFs and CPs with non‐fluorinated ligands, but significantly increased especially for fluoro substituents in α position and even more for perfluorinated ligands , . In this respect, it seems to be worthwhile to examine how the structural chemistry of uranium‐based CPs and MOFs develops, when fluorinated aromatic carboxylate ligands are introduced.…”

Two New MOFs Based on Cu2 Paddlewheel Units and Biphenyltetracarboxylate Ligands with a Different Degree of Fluorination

“…As described earlier fluorination of the phenyl rings in ortho position to the carboxylate group leads to an increased torsion angle between the latter and the plane of the phenyl ring due to repulsive interactions between the fluorine atom and the oxygen atoms of the carboxylate group and a reduced aromatic character of the C(phenyl)–COO – bond due to the electron withdrawing fluorine substituent , , . For UoC‐1(1F) this torsion angle was found to be 28.9(9)° and thus significantly larger than in HKUST‐1 and MOF‐505 (cp.…”

“…These angles are summarized in Table for UoC‐1(1F) and selected MOFs with a Cu 2 paddlewheel unit. For the enlarged torsion angles steric effects as well as electronic effects [reduced aromatic character of the C(phenyl)–COO – bond] are discussed , , . In CuMBTC and CuEBTC, methyl and ethyl groups, respectively, were introduced in ortho position to the carboxylate groups of a trimesate ligand .…”

Reproducible Synthesis of a Monofluorinated Trimesate: A Versatile Linking Ligand for the Construction of Lanthanide Coordination Polymers

“…[8a,8e, 16,17] cation three different structure types were obtained: 6 ] with Ln III = La (2), Ce (3), Pr (4), Nd (5), Sm (6), Eu (7), Gd (8) (14), Lu (15).…”