Syntheses, Characterization, and Luminescent Properties of Three 3D Lead−Organic Frameworks with 1D Channels

Three novel porous coordination polymers based on lead(II) and isonicotinic acid N-oxide, [Pb(INO)₂]₂·7H₂O (1), [Pb(INO)₂]·nH₂O (2), and [Pb₄(OH)₄(INO)₄]·nH₂O (3) (HINO = isonicotinic acid N-oxide), have been synthesized and characterized through single-crystal X-ray diffraction. Compound 1 features a most remarkable and unique three-dimensional (3D) framework with two distinct kinds of channels showing different sizes and shapes, which are occupied by two kinds of water clusters, according to the size and shape of the channels. Compound 2 possesses a 3D framework built up from one-dimensional (1D) Pb−O chains and INO ligands with 1D rectangular channels, in which lattice water molecules are located. The structure of 3 consists of [Pb₄(OH)₄]⁴⁺ cluster inorganic building blocks, which connect with μ₄-INO ligands through oxygen atoms from N-oxide moieties and carboxylate groups of INO to form 8.7 × 8.7 Ų rhombic channels running along the c-axis. In addition, the photoluminescence properties of coordination polymers 1−3 in the solid state have been reported. Gas adsorption properties of compound 3 have also been studied.