Fluorescent Arylphosphonic Acids: Synergic Interactions between Bone and the Fluorescent Core

Herein, we report the third generation of fluorescent probes (arylphosphonic acids) to target calcifications, particularly hydroxyapatite (HAP). In this study, we use highly conjugated porphyrin-based arylphosphonic acids and their diesters, namely 5,10,15,20-tetrakis[m-(diethoxyphosphoryl)phenyl]porphyrin (m-H8 TPPA-OEt8 ) and 5,10,15,20-tetrakis [m-phenylphosphonic acid]porphyrin (m-H8 TPPA), in comparison with their positional isomers 5,10,15,20-tetrakis[p-(diisopropoxyphosphoryl)phenyl]porphyrin (p-H8 TPPA-iPr8 ) and 5,10,15,20-tetrakis [p-phenylphosphonic acid]porphyrin (p-H8 TPPA), which have phosphonic acid units bonded to sp2 carbon atoms of the fluorescent core. The conjugation of the fluorescent core is thus extended to the (HAP) through sp2 -bonded -PO3 H2 units, which generates increased fluorescence upon HAP binding. The resulting fluorescent probes are highly sensitive towards the HAP in rat bone sections. The designed probes are readily taken up by cells. Due to the lower reported toxicity of (p-H8 TPPA), these probes could find applications in monitoring bone resorption or adsorption, or imaging vascular or soft tissue calcifications for breast cancer diagnosis etc.

Phosphonate Metal-Organic Frameworks: A Novel Family of Semiconductors

Herein, the first semiconducting and magnetic phosphonate metal-organic framework (MOF), TUB75, is reported, which contains a 1D inorganic building unit composed of a zigzag chain of corner-sharing copper dimers. The solid-state UV-vis spectrum of TUB75 reveals the existence of a narrow bandgap of 1.4 eV, which agrees well with the density functional theory (DFT)-calculated bandgap of 1.77 eV. Single-crystal conductivity measurements for different orientations of the individual crystals yield a range of conductances from 10^-3 to 10³ S m^-1 at room temperature, pointing to the directional nature of the electrical conductivity in TUB75. Magnetization measurements show that TUB75 is composed of antiferromagnetically coupled copper dimer chains. Due to their rich structural chemistry and exceptionally high thermal/chemical stabilities, phosphonate MOFs like TUB75 may open new vistas in engineerable electrodes for supercapacitors.

Alkali Phosphonate Metal-Organic Frameworks

A new family of porous metal-organic frameworks (MOFs), namely alkali phosphonate MOFs, is reported. [Na₂ Cu(H₄ TPPA)]⋅(NH₂ (CH₃ )₂ )₂ (GTUB-1) was synthesized using the tetratopic 5,10,15,20-tetrakis[p-phenylphosphonic acid] porphyrin (H₈ -TPPA) linker with planar X-shaped geometrical core. GTUB-1 is composed of rectangular void channels with BET surface area of 697 m²  g^-1 . GTUB-1 exhibits exceptional thermal stability. The toxicity analysis of the (H₈ -TPPA) linker indicates that it is well tolerated by an intestinal cell line, suggesting its suitability for creating phosphonate MOFs for biological applications.