Photoresponsive spin-crossover (SCO) compounds are particularly appealing due to precise adjustability of light wavelength/energy and the capability for remote switching. Herein, we introduce the 3-styrylpyridine (3-spy) ligand into a 2D Fe(II)–Ag(I) bimetallic Hofmann-type framework to construct a photoresponsive SCO compound [Fe(3-spy)₂{Ag(CN)₂}₂] (1). Upon irradiation at 365 nm, the criss-cross CC double bonds of 3-spy ligands in 1 undergo a pedal-like conformational motion and a photochemical [2 + 2] cycloaddition reaction, leading to structural disorder but resulting in a more regular coordination geometry around the SCO center in the cyclobutane product [Fe(hh-rctt-1,2-ppcb){Ag(CN)₂}₂] (2) (hh-rctt-1,2-ppcb = hh-rctt-1,2-bis(3-pyridyl)-3,4-bis(phenyl)cyclobutane, r = reference group, c = cis and t = trans, hh = head-to-head). These structural changes exert opposite influences on SCO cooperativity and the ligand field of the SCO center. Studies of SCO behavior under different irradiation times revealed that the SCO cooperative behavior gradually shifts from a two-step SCO in 1 to an incomplete and gradual one-step SCO in 2. Notably, T_1/2, which represents the intermediate spin state where γ_HS = 0.5, remains almost unchanged, indicating that only the SCO cooperativity is significantly modulated in this unique photochemical [2 + 2] reaction-integrated SCO system. Moreover, upon irradiation at 254 nm, partial stereoselective cleavage of the cyclobutane moieties in 2 was observed, suggesting the potential for constructing photoswitchable SCO materials.

Two-dimensional aluminophosphate is an important precursor of phosphate-based zeolites; a new Sun Yat-sen University No. 6 (SYSU-6) with |Hada|₂[Al₂(HPO₄)(PO₄)₂] has been synthesized in the hydrothermal synthesis with organic structure-directing agent (OSDA) of N,N,3,5-tetramethyladamantan-1-amine. In this paper, SYSU-6 is characterized by single-crystal/powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, transmission electron microscopy, infrared and UV Raman spectroscopy, solid-state ²⁷Al, ³¹P and ¹³C magic angle spinning (MAS) NMR spectra, and elemental analysis. The single-crystal X-ray diffraction structure indicates that SYSU-6 crystallized in the space group P2₁/n, with a = 8.4119(3), b = 36.9876(12), c = 12.5674(3), α = 90°, β = 108.6770(10)°, γ = 90°, V = 3704.3(2) ų, Z = 4, R = 5.12%, for 8515 observed data (I > 2σ(I)). The structure has a new 4,12-ring layer framework topology linked by alternating AlO₄ and PO₄ tetrahedra. The organic molecules reside between the layers and are hydrogen-bonded to the inorganic framework. The new type of layer provides a greater opportunity to construct zeolite with novel topology.

Reduction of Au ^III to Au ^I in a 2D Fe ^II –Au ^III Hofmann-type clathrate induces the distinct layer-stacking reorganization, switching the spin-crossover behavior from an abrupt one-step to a two-step process at lower temperature.