Chalcogen bonding in copper(ii)-mediated synthesis

Abstract

The chalcogen bond (ChB) is comparable to the hydrogen and halogen bonds both in terms of strengths and directionality. However, in contrast to the monovalent halogen atoms, usually the divalent...

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

“…However, upon coordination, the oxygen atoms of the acetate ligands simultaneously establish both ChB and hydrogen bonding (HB) interactions with the ligand. This is evident from the QTAIM analysis of the complex depicted in Figure 3b, where two bond critical points (BCPs) and bond paths (solid lines) connect the oxygen atoms of the acetate group to both the selenium and hydrogen atoms of the 5chloro-benzo[c] [1,2,5]selenadiazole. These intramolecular interactions serve a dual purpose: on the one hand, they obstruct one of the selenium σ-holes, and, on the other hand, they backdonate charge to the ligand, offsetting the electron-withdrawing effect of Cu (II).…”

“…For instance, for 1,2,5chalcogendiazoles and sulfathiazoles (as classic examples) systems, the following experimental and theoretical facts should be highlighted/considered: (i) tunability − replacement of the oxygen and sulfur atoms (poor ChB donors at BEOXAZ01 17 and BETHAZ01, 18 respectively) with Se or Te (strong ChB donors at BESEAZ01 19 and DEBHEY, 20 respectively) enhances the ChB strength (Scheme 1b); (ii) the strength and directionality of charge-assisted ChB at N + − Se•••Ha − increases by raising of nucleophilicity of the halide (Ha − ): I − < Br − < Cl − (see EFIWEW, 20 EFIWAS 21 and VEKYEQ 22 in Scheme 1c); (iii) cooperation of ChBs in a 4membered synthon of a supramolecular aggregate of 1,2,5chalcogendiazoles (Scheme 1d) leads to a substantial increase of the total binding strength (4, 7, or 17 kcal/mol for S, Se, or Te, respectively) in comparison to an individual version (synergic effect); 23 (iv) ChB can be strengthened by conjugation (resonance) in the π-system of a 5-membered synthon in sulfathiazoles (Scheme 1e), in the so-called resonance-assisted chalcogen bond (RAChB); 24 (v) attachment of substituents at R−Ch•••Nu can also alter the strength and directionality of ChB. For example, in contrast to the weak electron-donating −Ph and strong electron-accepting −I, −Br, and −Cl substituents, the strong electron donor − N(CH 3 ) 2 group at 4,7-disubstitutedbenzo[c] [1,2,5]selenadiazoles can completely disintegrate the common 4-membered Se 2 N 2 synthon since the nitrogen atom of this substituent acts as a strong ChB acceptor (compare SOLPIU, 25 ZANBUP, 26 ZANBOJ, 26 and GAXJUO 27 with XOQBUA 18 in Scheme 1f). Not only the electron-donating or -withdrawing character of R in R−Ch•••Nu but also its involvement in intermolecular interactions or coordination may alter the bond parameters of ChB.…”

“…Not only the electron-donating or -withdrawing character of R in R−Ch•••Nu but also its involvement in intermolecular interactions or coordination may alter the bond parameters of ChB. For example, the participation of the nitrogen atom of benzo[c] [1,2,5]selenadiazole (BESEAZ01) 19 in hydrogen (see GAJRAN) 28 or halogen (see GAJQUG) 28 bonding, as well as in coordination (see DEXTEI), 29 (ChB donor capability) of the selenium through aggregation of a catemer motif into the Se 2 N 2 supramolecular synthon (Scheme 1f). Due to the strong ChBs at the Ch 2 N 2 synthon, it has been used as a building block for the construction of supramolecular architectures with diverse functional properties.…”

“…cation−cation aggregation,64 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 2a); (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 2a,b); (iii) as expected, the coordination of N(2) at N(2)−Se(1)•••N(1) to Cu(II) (Figure 2) strengthened the ChB in 1, 2 and 5, whereas it was weakened in 3 and 4 (Scheme 2); (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;…”

Crystal structure and Hirshfeld surface analysis of (2Z)-3-oxo-N-phenyl-2-[(1H-pyrrol-2-yl)methylidene]butanamide monohydrate

“…Heterocyclic and carbocyclic aromatic systems are the most important compounds in organic chemistry (Gurbanov et al, 2017;Aliyeva et al, 2023). Organic synthesis is developing enormously with newer aromatic compounds having been obtained for diverse medicinal and commercial purposes (Maharramov et al, 2021;Poustforoosh et al, 2022;Gurbanov et al, 2022a,b).…”