Light-initiated reversible conversion of macrocyclic endoperoxides derived from half-sandwich rhodium-based metallarectangles

• Published in: Dalton transactions : an international journal of inorganic chemistry 2018, Vol.47 (8), p.2769-2777
• Main Authors: Shan, Wei-Long, Gao, Wen-Xi, Lin, Yue-Jian, Jin, Guo-Xin
• Format: Article
• Language: English
• Subjects: Anthracene; Conversion; Crystallography; Dimerization; Infrared spectroscopy; NMR; NMR spectroscopy; Nuclear magnetic resonance; Oxygenation; Photochemical reactions; Rhodium; Spectrum analysis
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c7dt03962j

Although reversible photo-dimerization or oxygenation of anthracene and its derivatives is a common reaction, light-initiated reversible conversion of endoperoxide organometallic frameworks has only rarely been addressed. Herein, a series of tetranuclear organometallic macrocycles, [Cp* 2 Rh 2 (μ-C 2 O 4 -κ O )] 2 (BP4VA) 2 (OTf) 4 ( 4 ), [Cp* 2 Rh 2 (BiBzIm)] 2 (BP4VA) 2 (OTf) 4 ( 5 ), and [Cp* 2 Rh 2 (DHBQ)] 2 (BP4VA) 2 (OTf) 4 ( 6 ), were obtained in good yields from the reactions of the binuclear half-sandwich rhodium precursors [Cp* 2 Rh 2 (μ-C 2 O 4 -κ O )Cl 2 ] ( 1 ), [Cp* 2 Rh 2 (BiBzIm)Cl 2 ] ( 2 ), and [Cp* 2 Rh 2 (DHBQ)Cl 2 ] ( 3 ) with the 9,10-bis(( E )-2-(pyrid-4-yl)vinyl)anthracene (BP4VA) ligand. The photochemical reaction of these metallarectangles was investigated by NMR and UV/vis spectroscopy. We have demonstrated that complexes 4 , 5 , and 6 can be reversibly and nearly quantitatively converted to the macrocyclic endoperoxides 4-O 2 , 5-O 2 , and 6-O 2 . Meanwhile, the structure of the endoperoxide photoproducts was unambiguously confirmed by 1 H/ 13 C NMR spectroscopy, IR spectroscopy, elemental analyses, and X-ray crystallography. A series of metallarectangles were synthesized by an anthracene-based ligand and three different half-sandwich rhodium precursors. The photochemical reactions show that these metallarectangles can be reversibly converted to the macrocyclic endoperoxides.