The assembly of organic radical anions between metal-borate scaffolds

Abstract

Metal–organic frameworks based on the Pb[B(Im)₄]⁺ unit form layered structures analogous to those observed in clays and double layered hydroxide minerals. These layers can act as scaffolds for the organization of anionic organic guests. In this report, we use this scaffold to assemble TEMPO and PROXYL carboxylates in the interlayer spacings of Pb[B(Im)₄](4-carboxy-TEMPO) 1 and Pb[B(Im)₄](3-carboxy-PROXYL)(H₂O) 2, respectively. The resultant materials are paramagnetic, and the organization of the radical units differs between the two compounds. This results in changes in electronic structure of the radical unit, as observed by EPR spectroscopy.