Trifluoroethoxy‐Coated Subphthalocyanines Attract Small Arenes in Their π‐Concave Cavity

Abstract

What is the most significant result of this study?Small aromatic molecules such as benzene and toluene are often liquid at room temperature. Thus the X-ray crystallographic analysis of these non-crystalize, liquid-type small aromatics are fundamentally difficult. We found that fully substituted subphthalocyanine (SubPc) derivatives having trifluoroethoxy groups at their peri-positions tend to clasp as mall arene molecule at their 14 pelectron conjugated concave to generate 1:1a rene clathrates, which are easily crystallized. Thus, the trifluoroethoxy-substituted SubPc could be useful tools for binding small arenes in the concave cavity leading to X-ray crystallographic analysis of non-crystallized arenes as their clathrates. DFT calculations of the SubPc/arene clathrates revealed that dispersion interactions are the major impetus for clathrate formation while the contributions of fluorine effects and electrostatic interactions to the attraction are not large.

Recent advances in subphthalocyanines and related subporphyrinoids

“…1 Several novel crystal structures of SubPc derivatives have been published since then, which are reported in ref. 17, 19, 30, 32, 43, 56, 57, 79, 85–88, 91, 96, 97, 108, 111, 114, 121, 130, 132, 141, 143, 145, 165, 172, 180 and 182–185. Selected data from X-ray diffraction analysis of some of these crystal structures are reported in Table 1.…”

“…Crystal polymorphs of SubPcs that show inclusion of aromatic solvent molecules (toluene, DCB) within the cavity of the macrocycle have been reported. 11,19,185 Single-crystal XRD analysis of chiral peripherally trihalogenated SubPcs, namely β-F 3 SubPc-Cl, α-F 3 SubPc-Cl, β-Cl 3 SubPc-Cl and α-Cl 3 SubPc-Cl, showed that these derivatives co-crystallized as mixtures of the C 1 and C 3 regioisomers forming solid-state mixed alloyed compositions. 239…”

“…43 Remarkably, the X-ray crystal structure of a SubPc cation having a weakly coordinating carborane anion has also been reported, showing the tendency of the central boron to adopt a planar geometry, as expected for a tricoordinated B atom. 186 The crystal structures of some covalently linked SubPc dimers 72,75,79,127,128,151,185 and fused SubPc-containing hybrid dimers 129,187,188 have also been reported.…”

Analysis of the solvent effects on the crystal growth of peripherally chlorinated boron subphthalocyanines

“…For our study, we then began by looking through the Cambridge Crystallographic Data Centre (CCDC) and found that several solvents were incorporated into determined BsubPc single crystals: DCM, 36,[44][45][46][47][48][49] CHCl 3 , 50-58 H 2 O, 49,50,52,55,[59][60][61][62] acetone, 63 THF, 57,63 hexane, 64,65 and heptane. 66,67 Furthermore, aromatic solvents were also used for BsubPc crystal growth and found to be incorporated into their determined nano-structures, such as benzene, 23,35,36,52,56,[68][69][70][71] toluene, 53,56,[72][73][74][75] chlorobenzene, 15 and dichlorobenzene. 62,76 For a more in-depth example, a report outlines that the solvent is incorporated into the crystals when attempting to co-crystallize a BsubPc with a fullerene.…”

“…69,72,73,76 In another example, Mori et al synthesized a fully peripherally trifluoroethoxy substituted BsubPc, where they found that peripheral ligands would flexibly surround toluene or benzene, respectively, when using slow evaporation as the method of crystallization. 75 Mori et al also fabricated a m-oxo hetero-dimer where one of the BsubPcs was a fully trifluoroethoxy substituted BsubPc and the other was unsubstituted. The trifluoroethoxy substituted BsubPc encapsulated one molecule of the aromatic solvent, whereas the unsubstituted BsubPc formed a 2 : 1 sandwich complex trapping one molecule of toluene between two unsubstituted BsubPcs.…”