Nanoscale Two-Dimensional FeII- and CoII-Based Metal-Organic Frameworks of Porphyrin Ligand for the Photodynamic Therapy of Breast Cancer.

The delivery of biocompatible reagents into cancer cells can elicit an anticancer effect by taking advantage of the unique characteristics of the tumor microenvironment (TME). In this work, we report that nanoscale two-dimensional FeII- and CoII-based metal-organic frameworks (NMOFs) of porphyrin ligand meso-tetrakis (6-(hydroxymethyl) pyridin-3-yl) porphyrin (THPP) can catalyze the generation of hydroxyl radicals (•OH) and O2 in the presence of H2O2 that is overexpressed in the TME. Photodynamic therapy consumes the generated O2 to produce a singlet oxygen (1O2). Both •OH and 1O2 are reactive oxygen species (ROS) that inhibit cancer cell proliferation. The FeII- and CoII-based NMOFs were non-toxic in the dark but cytotoxic when irradiated with 660 nm light. This preliminary work points to the potential of porphyrin-based ligands of transition metals as anticancer drugs by synergizing different therapeutic modalities.

Similarities and differences between Mn(II) and Zn(II) coordination polymers supported by porphyrin-based ligands: synthesis, structures and nonlinear optical properties.

Four coordination polymers (CPs) Mn-TMPP (1), Zn-TMPP (2), Mn-THPP (3), and Zn-THPP (4) have been synthesized and characterized (H2TMPP = meso-tetrakis (6-methylpyridin-3-yl) porphyrin; H2THPP = meso-tetrakis (6-(hydroxymethyl) pyridin-3-yl) porphyrin). The one-dimensional (1D) chain compound 1 is formed via a head-to-tail connection of the Mn-TMPP unit, wherein the central Mn2+ features a square pyramidal geometry coordinated by four N atoms from the porphyrin skeleton and one additional N atom from an adjacent Mn-TMPP unit. Compound 2 features an octahedral Zn2+ center associated with four N atoms from the porphyrin skeleton to define the equatorial plane and two additional N donors at the axial positions to give a two-dimensional (2D) CP. The 1D chain of 1 and the 2D layer of 2 possess distinctive molecular structures but nearly identical molecular arrangements in their unit cells viewed along all three crystallographic axes. By contrast, Mn- and Zn-based CPs 3 and 4 supported by the THPP ligand share both identical molecular connectivities and crystal packing. In 3/4, each Mn/Zn center is chelated by four N donors of the porphyrin interior to define the equatorial plane of an octahedron, whose axial sites are occupied by two alcoholic OH groups from a pair of trans-located pyridinemethanol moieties. The third-order nonlinear optical properties of 1-4 investigated using the Z-scan technique at 532 nm revealed reverse saturable absorption and self-focusing effects for all four CPs, with hyperpolarizability values (γ) in the range 1.42 × 10-28 esu to 7.64 × 10-28 esu. These high γ values are comparable to the best porphyrin-based molecular assemblies, demonstrating potential for these materials in optical limiting applications.

Zinc and Cadmium Complexes of Pyridinemethanol Carboxylates: Metal Carboxylate Zwitterions and Metal-Organic Frameworks.

The heterofunctional lactone furo[3,4-b]pyridin-5(7H)-one (L1 ) undergoes a coordination-induced ring-opening reaction with Zn(NO3 )2 ⋅ 6H2 O to yield the zwitterionic [Zn(L1 ')2 (H2 O)2 ] (1, L1 '=2-(hydroxymethyl)nicotinate) with an uncoordinated carboxylate. The same reaction with Cd(NO3 )2 ⋅ 4H2 O provides a two-dimensional (2D) network of [Cd(L1 ')2 ]n (3) with the carboxylates coordinated to cadmium(II) propagating the assembly. The corresponding reactions of Zn(NO3 )2 ⋅ 6H2 O and Cd(NO3 )2 ⋅ 4H2 O with 2-(hydroxymethyl)isonicotinic acid (HL2 ) generated zwitterionic [Zn(L2 )2 (H2 O)2 ] (2) and a 2D network [Cd(L2 )2 ]n ⋅nDMF (4, DMF=N,N'-dimethylformamide), respectively. Complexes 1-4 are weakly emissive, giving ligand-centered emissions at 409 nm (1), 412/436 nm (2), 404 nm (3), and 412/436 nm (4) in CHCl3 solutions upon excitation at 330 nm. This work points to the potential of using 'hidden' functionalities widely found in small organic molecules and natural products for the construction of coordination complexes with new functionality and potential applications.

Morphology-dependent third-order optical nonlinearity of a 2D Co-based metal-organic framework with a porphyrinic skeleton.

A two-dimensional (2D) Co-based metal-organic framework (MOF) with porphyrinic skeleton forms crystalline plates, flower-shaped clusters, and ultrathin films under optimized conditions, including the use of polyvinylpyrrolidone (PVP) as a surfactant. Ultrathin films demonstrate the best solution-based third-order nonlinear optical properties, featuring a nonlinear transmittance (T) value of 0.54, absorption coefficient (α2) of 9.5 × 10-10 m W-1 and second hyperpolarizability (γ) value of 1.37 × 10-28 esu, which are slightly better than those of the flower-shaped clusters (T = 0.65, α2 = 7.0 × 10-10 m W-1; γ = 1.27 × 10-28 esu), but marginally better than those of the crystalline thin plates (T = 0.94, α2 = 2.4 × 10-10 m W-1; γ = 0.24 × 10-28 esu).

Effective loading of cisplatin into a nanoscale UiO-66 metal-organic framework with preformed defects.

Defects within the nanoscale UiO-66 metal-organic framework (MOF) are created to lock a hybrid phosphonoacetate ligand through Zr-O-P linkages, leaving the carboxyl group free to anchor cisplatin prodrug cis, cis, trans-[Pt(NH3)2Cl2(OH)2]. A drug loading of 256.5 mg g-1 (25.7 wt% based on cisplatin) was achieved with a Zr6 : Pt : P ratio of 1.5 : 1 : 1, which surpasses defect-free UiO-66 and several other MOF carriers. This framework exhibited a burst release of its payload in PBS solution in the first 2 h, releasing 71% of the drug, including a 50% payload release in less than 1 h. This work demonstrates that MOF defects can be intentionally engineered to achieve a high drug loading, and serves as an alternative to drug encapsulation using the pore void and through the association of the functionalized ligand.