Search

Heteroatom-doped organic π-conjugated molecules (OCMs) have become one type of emerging optoelectronic material with intriguing functionalities. Phosphorus (P)-doped OCMs are a special member of heteroatom-doped OCMs where rich P-chemistry is able to fine-tune their optoelectronic properties. Herein, we report a new series of nonplanar diazaphosphepine-based polycyclic aromatic heterocycles (DPP-PAHs). Efficient and mild double P–N cyclization allowed one to readily incorporate two P-centers in DPP-PAHs. With nonplanar diazaphosphepine rings, DPP-PAHs exhibit contorted structures in single crystal structures. The functionalization of double P-centers by H2O2 and S8 gave DPP-PAHs with P＝O and P＝S centers, respectively. Compared with the parent small molecule, the DPP-PAHs exhibit high photoluminescence quantum yields. Our experimental and theoretical studies further revealed that both P-environments and conjugated backbones have impacts on the photophysical properties of the DPP-PAHs. [ABSTRACT FROM AUTHOR]

Six Zn/Cd metal–organic frameworks (MOFs), {[Zn2(dppa)(bpy)2(H2O)]·H2O}n (1), {[Zn2(dppa)(phen)2(H2O)]·3H2O}n (2), [Cd(H2dppa)(bpy)]n (3), {[Cd2(dppa)(dye)]·H2O}n (4), {[Cd4(dppa)2(H2O)9]·H2O}n (5) and {[Cd2(dppa)(bpe)2(H2O)]·H2O}n (6) (H4dppa = 5-(3′4′-dicarboxylphenoxy)isophthalic acid, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine, dye = 2,2′-dipyridylamine, bpe = 1,2-bis(4-pyridy) ethane), were synthesized and structurally characterized by elemental analyses, plasma (ICP) spectrometry, IR spectroscopy, and single-crystal X-ray diffraction analyses. 1–3 are 1D ring chains. 4 shows a 2D bilayer network based on a tetranuclear cadmium cluster linked by (dppa)4− ligands. 5 displays a 2D bilayer network based on a trinuclear cadmium cluster, in which (dppa)4− ion shows two different coordination modes. In contrast to the above MOFs, 6 possesses a 3D network structure based on dinuclear cadmium units cross-linked by (dppa)4− and bpe ligands. For 1–6, weak hydrogen bonding and π⋯π stacking contacts link the discrete 1D chains or 2D networks to form high-dimensional supramolecular structures. Especially, in 1–6, (dppa)4− ligand displays seven different coordination modes and conformations, which may show natural synergy in the structural diversity of the resulting MOFs. The remarkable characteristic of these frameworks is that 2 demonstrates highly selective and sensitive bifunctional luminescent sensing towards acetone and Fe3+ ion. In addition, the thermal stabilities and luminescence properties of the MOFs were studied. [ABSTRACT FROM AUTHOR]