We demonstrate how a single-crystal to single-crystal transformation resulting from bridging-linker replacement is possible in extended 2D and 3D metal-organic frameworks (MOFs) by introducing pillared paddlewheel MOF structures into a solution containing dipyridyl linkers. No lateral movement of the layers was observed during this transformation, creating a templating effect from the "parent" structure to the "daughter" structure. A previously unattainable structure was obtained by a two-step synthetic method utilizing the bridging-linker replacement transformation method. Additionally, a bridging-linker insertion was observed when excess linker was used with the 2D MOF structure, inducing an overall 2D to 3D transformation.

We report three new porphyrin-based, pillared paddle-wheel homologous series: porphyrin paddle-wheel frameworks PPF-3, -4, and -5. These compounds are assembled from free base or palladium tetrakis(4-carboxyphenyl)porphine, M(NO(3))(2) (M = Co and Zn), and 4,4'-bipyridine via solvothermal reactions. The resulting solids exhibit 3D metal-organic frameworks, where 2D layers are pillared by bipyridine with three different packing arrangements.

A thermoresponsive, 3D hinged metal-organic framework (HMOF-1) assembled from meso-tetra(4-pyridyl)porphine and CdI(2) exhibits a 3D "lattice fence" topology with extraordinary thermal expansion and shrinkage. A simple structural model is established to elucidate such a drastic thermal response. The hinged structure model presented here can also be applied to other "lattice fence" topologies with little or no modification, depending on the symmetry of the molecular building blocks.

The UV−vis spectra, emission spectra and lifetimes, transient absorption characteristics, and optical limiting performances of three binuclear cyclometalated platinum(II) 4,6-diphenyl-2,2‘-bipyridine complexes with bis(diphenylphosphino)methane (dppm), bis(diphenylphosphino)ethane (dppe), and bis(diphenylphosphino)propane (dppp) bridging ligands have been investigated. All three complexes exhibit concentration-dependent photoluminescence in CH3CN at room temperature and 77 K, and the emission energy is affected by the length of the bridging ligand. [Pt2L2(μ-dppm)](ClO4)2 (1) (L = 4,6-diphenyl-2,2‘-bipyridine) shows a broad, structureless emission band at about 667 nm when the complex concentration is higher than 6.0 × 10-5 mol/L, which can be attributed to a 3[dσ*,π*] state due to metal−metal interactions. [Pt2L2(μ-dppe)](ClO4)2 (2) and [Pt2L2(μ-dppp)](ClO4)2 (3) essentially exhibit no metal−metal interactions between the two platinum centers, and their emission can be ascribed to a 3MLCT (metal-to-ligand charge transfer) excited state. The emission lifetime is approximately 200 ns for 1 at 1.2 × 10-4 mol/L, ∼1.5 μs for 2 at 1.4 × 10-4 mol/L, and ∼2.0 μs (68%) and ∼0.4 μs (32%) for 3 at 1.3 × 10-4 mol/L. All complexes show moderately intense, broad positive transient difference absorption bands from near-UV and extending to near-IR spectral regions. The nonlinear transmission experiment at 532 nm using 4.1 ns laser pulses demonstrates that 2 and 3 exhibit stronger optical limiting for nanosecond laser pulses than SiNc, which is likely associated with their very low ground-state absorption cross sections and relatively long triplet excited-state lifetimes (approximately microseconds).