Colorimetric and Fluorescent Chemosensors for the Detection of 2,4,6‐Trinitrophenol and Investigation of their Co‐Crystal Structures

A full account of our studies of 2,4,6‐trinitrophenol (TNP) sensing is provided. A series of chemosensors 2 , 3 , 4 , 5 with a variety of aromatic chromophores for specific recognition of TNP has been designed and then realized through the fluorescence “on/off” mechanism. These chemosensors demonstrated highly selective, sensitive, and fluorescent quenching of TNP with remarkable visual changes through the intramolecular charge‐transfer (ICT) process. Their host–guest interactions were investigated by ¹H NMR spectroscopic titrations and their corresponding co‐crystal structures, which showed that the 1:1 host–guest complexes were formed by multiple hydrogen‐bond interactions in solution or in the solid state. The origins of the significant affinity demonstrated during the fluorescence recognition process were further disclosed through DFT calculations of corresponding compounds.     

Similar Coordination – Different Dimensionality: Synthesis,Single Crystal Structures,and Theoretical Studies of Hydrogen‐bonded {[Ca(H2O)2L4]I2}n/∞ (1: L = CH3COOC2H5, n = 1; 2: L = OC4H8, n = 2)

CaI₂(H₂O)₂ reacts with O‐donor ligands L to yield coordination compounds of the type {[Ca(H₂O)₂L₄]I₂}_n/∞, ( 1 : L = CH₃COOC₂H₅, n = 1; 2 : L = THF, n = 2). Both compounds feature a coordination number of six around the calcium atom with two water molecules in axial positions and four ligands L in equatorial positions of a tetragonal bipyramid. Due to only a slight variation in the arrangement of the cationic units [Ca(H₂O)₂L₄]²⁺, hydrogen bonds can be built up between them and the iodide anions in different ways in order to lead to a one‐dimensional polymer for 1 and a two‐dimensional polymer for 2 . Density functional theory calculations provide useful informations on the involved orbitals on the μ₂‐bridging iodide and on the structure of the systems, leading to a small H–I–H angle of 71.2° in 1 compared to a large H–I–H angle of 121.8° in 2 .