Ligand Steric Hindrances Switch Bridging (μ₂-I)···O,O to Two-Center I···O Halogen-Bonding Mode in the Assembly of Diketonate Copper(II) Species

Abstract

The diketonate complex [Cu{OC( t Bu)CC(H)O} 2 ] (1) and its cocrystals with 1,4-diiodotetrafluorobenzene (1,4-FIB), 1,3,5-triiodotrifluorobenzene (1,3,5-FIB), and 1,4-dioxane were studied by X-ray diffraction. In the solid state, 1 exhibits the cis-geometry with syn-t Bu groups; the geometry is stable in storage at 20−25 °C or even in heating in the solid state, solutions, or sublimation. The DFT modeling for isolated molecules of cis-and trans-1 revealed that the cis-form is only slightly more energetically favorable. However, cocrystals trans-1FIB, and trans-1•1,3,5-FIB•C 4 H 8 O 2 display the trans-geometry with the anti-t Bu substituents; the comparison of the geometries revealed the facile crystalpacking-driven cis-to-trans isomerization of 1 upon the cocrystal growth. Compared to the cocrystals of the unsubstituted [Cu(acetylacetonate) 2 ] complex with the FIBs, in the assembled architectures of trans-1•1,4-FIB and trans-1•1,3,5-FIB•C 4 H 8 O 2 , the switch from the bridging (μ 2 -I)•••O,O to two-center I•••O halogen bonding is demonstrated. The theoretical study revealed that the energetic features of the (μ 2 -I)•••O,O halogen bonding in [Cu(acetylacetonate) 2 ]•1,4-FIB are similar to those of the I•••O halogen bonding in 1•1,4-FIB. Variable-temperature XRD data (at 100, 150, 200, 250, and 300 K) for cis-1 and trans-1•1,4-FIB indicate that the infinite chains of molecules stabilized by I•••O halogen bonding remain the main packing motif at all applied temperatures.

Combined σ- and π-Hole Donor Properties of Perfluorinated Iodo(or bromo)benzenes: Halogen Bonding and π-Hole Interactions in Cocrystals Including Cu4I4 Clusters

“…In view of our interest in the chemistry of dialkylcyanamides − and also in crystal engineering involving coinage metal complexes, − we attempted to crystallize CuI with the dialkylcyanamides NCNR 2 (R 2 = Me 2 , Et 2 , C 4 H 8 , C 5 H 10 , C 4 H 8 O) in the presence of such mixed σ-/π-hole donors as 1,4-FIB or 1,4-FBrB. Despite our repeated attempts, only experiments with the system CuI/NCNMe 2 /halo­(perfluoro)­arenes in MeCN gave cocrystals 1 ·1,4-FIB, 2 ·1,4-FIB, and 1 ·1,4-FBrB; they all were studied by XRD.…”

Supramolecular Aggregation of Lead(Ii) Perchlorate and a Thiosemicarbazide Derivative Linked by a Myriad of Non-Covalent Interactions

“…For the S••• N,O contacts, a different equation proposed in the literature was used [47,48] (E dis = -0.556 × V r ). This equation has been successfully used before in a variety of halogen bonding interactions [49][50][51][52][53][54][55][56]. The obtained results show that the hydrogen bonds involving the acetonitrile are slightly stronger (1.09 kcal/mol and 0.72 kcal/mol) than those involving the aromatic ring (0.63 kcal/mol and 0.53 kcal/mol) (Table 3).…”

On the Importance of Halogen Bonding Interactions in Two X-ray Structures Containing All Four (F, Cl, Br, I) Halogen Atoms

“…We used the equation E = 0.556*V r to estimate the association energy of each HaB. This equation has been successfully used before in a variety of halogen bonding interactions [41][42][43][44][45][46][47][48][49]. As a result, the association energy of HaB "a" is −1.67 kcal/mol, HaB "b" is −0.78, and HaB "c" is −0.88 kcal/mol.…”