The reaction of 1-trifluoromethyl-3-(1′-pyreno)-1,3-propanedione with lanthanum(III) trichloride in the presence of pyridine leads to halide ligand exchange, yielding a novel pyridinium tetrakis{1-trifluoromethyl-3-(1′-pyreno)-1,3-propanedionato}lanthanate(III) complex with four polycyclic aromatic hydrocarbon moieties. This reaction easily proceeds under mild conditions (25°C, 24？h) producing the complex in a 90% isolated yield. The complex was characterized by infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and positive fast atom bombardment mass spectrometry, and its precise structure was determined by single crystal X-ray diffraction. Ultraviolet-visible spectroscopy, fluorescence spectroscopy, and X-ray analysis demonstrated that the four pyrene moieties were independently oriented. 1. Introduction In recent years, lanthanide(III) complexes with β-diketonato ligands consisting of various aromatic components have attracted numerous researchers [1]. These compounds represent well-known electronic and luminescent materials with numerous applications in material chemistry [2–4]. In addition, polycyclic aromatic hydrocarbons (PAHs), such as pyrene and perirene, have been highlighted by numerous researchers because of their electronic and luminescent properties [5–9]. From our recent work, the structures of the octadentate lanthanide(III) complex derived by X-ray analysis were reported to be unexpectedly cone-like [10]. The present study focuses on the synthesis and investigation of the structural properties of the novel octacoordinate lanthanum(III) complex with four bidentate β-diketonato ligands having four PAH (pyrene) moieties and one pyridinium ion as a counter cation. We also confirmed the exact structure of the octadentate lanthanide coordination complex having highly aggregated PAHs by X-ray analysis. 2. Materials and Methods All the reagents and solvents were obtained from commercial sources and were used as received. Infrared spectra were recorded on a HITACHI FT-IR 410X instrument using the KBr method. Proton nuclear magnetic resonance (1H-NMR) spectra were obtained on a Bruker 400？MHz Avance400S spectrometer at 293？K in chloroform-d3 using tetramethylsilane (Me4Si) as an internal reference. Positive fast atom bombardment mass spectrometry (pos. FAB-MS) spectra were obtained on a Noppon Densi JEOL JMS-SX102A spectrometer using nitrobenzylalcohol (NBA) as the matrix and dichloromethane (DCM) as the solvent. This instrument was operated in the positive ion mode using an m/z range of 100–2000. Elemental analysis was
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