Self-assembly of functional macrocyclic metal complexes and 4-(phenylazo)benzoic acid: preparation, structure, and photoluminescence

Light-induced Photoswitching of 4-(Phenylazo)benzoic Acid on Au(111)

Photochromic molecules can undergo a reversible conversion between two isomeric forms upon exposure to external stimuli such as electromagnetic radiation. A significant physical transformation accompanying the photoisomerization process defines them as photoswitches, with potential applications in various molecular electronic devices. As such, a detailed understanding of the photoisomerization process on surfaces and the influence of the local chemical environment on switching efficiency is essential. Herein, we use scanning tunneling microscopy to observe the photoisomerization of 4-(phenylazo)benzoic acid (PABA) assembled on Au(111) in kinetically constrained metastable states guided by pulse deposition. Photoswitching is observed at low molecular density and is absent in tight-packed islands. Furthermore, switching events were noted in PABA molecules coadsorbed in a host octanethiol monolayer, suggesting an influence of the surrounding chemical environment on photoswitching efficiency.

Crystal structure of [3,10-bis-(4-fluoro-pheneth-yl)-1,3,5,8,10,12-hexa-aza-cyclo-tetra-deca-ne]nickel(II) diperchlorate

The square-planar nickel(II) title complex, [Ni(C24H36F2N6)](ClO4)2 or [NiL](ClO4)2 (L = 3,10-bis-(4-fluoro-pheneth-yl)-1,3,5,8,10,12-hexa-aza-cyclo-tetra-deca-ne) was synthesized by a one-pot reaction of template condensation and its X-ray crystal structure was determined. The nickel(II) ion lies close by a twofold axis and the complex displays whole-mol-ecule disorder. Ligand L, a hexa-aza-cyclo-tetra-decane ring having 4-fluoro-phenethyl side chains attached to uncoordinated nitro-gen atoms, adopts a trans III (R,R,S,S) configuration. The average Ni-N bond distance is 1.934 (9) Å, which is quite similar to those of other nickel(II) complexes with similar ligands. The nickel(II) ion is located 0.051 (7) Å above the least-squares plane through the four coordinated N atoms. The average C-N bond distance and C-N-C angle involving uncoordinated nitro-gen atoms are 1.425 (12) Å and 118.0 (9)°, respectively, indicating a significant contribution of sp 2 hybridization for these N atoms. The inter-molecular N-H⋯O, C-H⋯O/F hydrogen bonds of the complex form a network structure, which looks like a seamless floral lace pattern.

Crystal structure of 2-oxopyrrolidin-3-yl 4-(2-phenyl-diazen-1-yl)benzoate

In the title compound, C17H15N3O3, the plane of the pyrrolidone ring is inclined at an angle of 59.791 (2)° to that of the azo-benzene segment, which adopts a configuration close to planar. In the crystal, mol-ecules are oriented pairwise by (2-oxopyrrolidin-3-yl)-oxy moieties at an angle of 76.257 (3)°, linked by hydrogen bonds and π-stacking inter-actions, forming zigzag supra-molecular chains parallel to [010] further linked via additional C-H⋯π inter-actions.

Synthesis and characterization of a macrocyclic copper complex containing the 14-membered 1,3,5,8,10,12-hexaazacyclotetradecane unit

In this work, a new macrocyclic copper complex, [Cu(ACE)(SCN)2]; ACE: 1,3,6,10,12,15-hexaazatricyclo[13.3.1.16,10]eicosane, was prepared and characterized by elemental analysis, FT-IR, Raman spectroscopy and single-crystal X-ray diffraction. X-ray analysis of [Cu(ACE)(SCN)2] reveals an elongated octahedral geometry around the copper atom in a centrosymmetric CuN6 environment.