Preparation of double decker {Li3(Cl−)(Hhp)}22− dianions and H2TPCor− monoanions by deprotonation of free-base trithiododecaazahexaphyrin (H3Hhp) and triphenylcorrole (H3TPCor) macrocycles

Abstract

Deprotonation of free-base [30]trithia-2,3,5,10,12,13,15,20,22,23,25,30-dodecaazahexaphyrin (hemihexaphyrazine, H3Hhp) and 5, 10, 15- triphenylcorrole (H3TPCor) macrocycles by an excess of lithium diethylamide, LiNEt2, in the presence of three equivalents of cryptand[2.2.2] has been studied. Crystallization of the obtained products after the reaction allows the isolation of crystalline {Cryptand[2.2.2](Li)}2{Li3Cl(Hhp)}2·6C6H4Cl2 (1) and {Cryptand[2.2.2](Li)} {H2TPCor)·0.5C6H4Cl2 (2) salts. Compound 1 is the first example of lithium derivative of hemihexaphyrazine which additionally coordinates one Cl− anion per three lithium ions. There are five (Li+)⋯(Cl−) contacts of 2.389(4)-2.456(4) Å length for two independent {Li3Cl(Hhp)}− anions. However, one contact elongates to 2.557(4) Å due to shift of Cl− anions towards two hydrogen atoms of cryptand[2.2.2] providing the formation of weak hydrogen (Cl−)⋯H(cryptand) bonds. Two {Li3Cl(Hhp)}− anions are arranged in the double decker {Li3Cl(Hhp)}22− structure due to that the Cl− anion of one Li3Cl(Hhp) unit forms additional weak (Li+)⋯(Cl−) contacts of 2.586–2.617(4) Å with two lithium ions of the second {Li3Cl(Hhp)}− unit. In contrast to H3Hhp, H3TPCor splits only one hydrogen atom at deprotonation in the same experimental conditions forming a planar H2TPCor− anion and, therefore, H3Hhp has higher acidity of central hydrogen atoms in comparison with H3TPCor. Deprotonation preserves diamagnetic state of pristine macrocycles in salts 1 and 2. Their optical properties are also discussed. DFT calculations were carried out for 1 to discuss aromaticity of the macrocycles, electronic structure and optical spectrum of 1.