Acid‐Base and Anion Binding Properties of Tetrafluorinated 1,3‐Benzodiazole, 1,2,3‐Benzotriazole and 2,1,3‐Benzoselenadiazole

Abstract

Dedicated to Prof. Alexandra M. Z. Slawin on the occasion of her 60 th birthday.The influence of fluorination on the acid-base properties and the capacity of structurally related 6-5 bicyclic compounds -1,3-benzodiazole 1, 1,2,3-benzotriazole 2 and 2,1,3-benzoselenadiazole 3 to σ-hole interactions, i. e. hydrogen (1 and 2) and chalcogen (3) bondings, is studied experimentally and computationally. The tetrafluorination increases the Brønsted acidity of the diazole and triazole scaffolds and the Lewis acidity of selenadiazole scaffold decreases the basicity. Increased Brønsted acidity facilitates anion binding via the formation of hydrogen bonds; particularly, tetrafluorinated derivative of 1 (compound 4) binds Cl À . Increased Lewis acidity of tetrafluorinated derivative of 3 (compound 10), however, is not enough for binding with Cl À and F À via chalcogen bonds in contrast to previously studied Te analog of 10. It is suggested that the maximum positive values of molecular electrostatic potential at the σ-holes, V S,max , can be a reasonable metric for design and synthesis of new anion receptors with selenadiazole-diazole/ triazole hybrids as a special target. Related chlorinated compounds are also discussed.

Halide Complexes of 5,6‐Dicyano‐2,1,3‐Benzoselenadiazole with 1 : 4 Stoichiometry: Cooperativity between Chalcogen and Hydrogen Bonding

“…Therefore, taking into account previous results [72–86] and very tentatively, the 1 +[Hal] − ↔[ 1 −Hal] − equilibrium (Scheme 2) can be assumed for the reaction mixtures, with the formation/synthesis of [ 1 4 −Hal] − occurring during crystallization of the isolated products employing HB . In this particular study, the conventional solution NMR and ESI‐MS, which typically are reliable and informative, [40,72–74,76,78,104] yielded limited results. With variable‐temperature 35 Cl and ambient‐temperature 77 Se NMR, only the fact of interaction between 1 and [Hal] − in solution was confirmed; whereas with ESI‐MS, no anionic complexes were detected (SI).…”

“…Comparison with reference compounds 3 – 7 [72,104] suggests that V S,max values for the σ‐holes of 1 and 2 are high enough for this series (Scheme 1, Table 1) whose members, e. g. 6 , [72] actually form ChB ‐bonded [Hal] − complexes; or, e. g. 7 , can form those with various charged and neutral Lewis bases according to theoretical estimations [51,73,74,80,81,89,105,106] . Despite electrostatics is not the only contribution in the ChB , and comparison of V S,min values is rather simplifying, the MEPs analysis suggests that compounds 1 and 2 are promising for the field.…”

“…However, their [Hal] − complexes are expected to be weaker bound than those of compound 6 [72] . For compounds 3 and 5 with smaller V S,max values than for 1 and 2 complexation with [Hal] − was observed neither in solutions nor in the crystalline phases [104] …”

“…[72] For compounds 3 and 5 with smaller V S,max values than for 1 and 2 complexation with [Hal] À was observed neither in solutions nor in the crystalline phases. [104] Scheme 1. Selenadiazoles 1-7.…”

Substituent Effect on Chalcogen Bonding in 5-Substituted Benzo[c][1,2,5]selenadiazoles and Their Copper(II) Complexes: Experimental and Theoretical Study

“…ChB-assisted aggregation of chalcogenodiazoles into a 4-membered Se 2 N 2 supramolecular ring has been well explored as an effective synthon for the design of functional materials such as new supramolecular capsules, π-conjugated polymers, organic solar cells or semiconductors, − anion binding, cation–cation aggregation, etc. The effect of substituents on ChB strength at the supramolecular Se 2 N 2 synthon of 5-substituted benzo­[ c ]­[1,2,5]­selenadiazoles and their copper­(II) complexes were investigated in this work and the following conclusions should be highlighted: (i) both electron donating (X = −CH 3 ) and withdrawing (X = −F, −Cl, −Br or −NO 2 ) groups can aggregate a catemer motif of benzo­[ c ]­[1,2,5]­selenadiazole (X = −H) into the Se 2 N 2 supramolecular synthon (Scheme a); (ii) the substituents alter the Se ··· N distance or ∠N–Se ··· N angle in the Se 2 N 2 synthon in the crystal structure of ligands and their Cu­(II) complexes, but there is no clear trend between the ChBs strength or directionality and the Hammett’s para -substituent constant (Scheme a,b); (iii) as expected, the coordination of N(2) at N(2)–Se(1) ··· N­(1) to Cu­(II) (Figure ) strengthened the ChB in 1 , 2 and 5 , whereas it was weakened in 3 and 4 (Scheme ); (iv) the energy of various types of intermolecular noncovalent interactions through involvement of substituents can compete with their electronic effect (σ p ) in the crystal structure of 5-substituted benzo­[ c ]­[1,2,5]­selenadiazoles and its complexes 1 – 5 , resulting in no clear relationship between σ p and the ChB strength or directionality; (v) theoretical DFT calculations were employed to uncover the moderately strong character of ChBs while also revealing that Cu-coordination exerts only a minimal influence on the strength of these interactions.…”