Silver and gold luminescent metallomesogens based on pyrazole ligands

Abstract

A series of ionic bis(pyrazole)-silver(I) and -gold(I) complexes [ML(2)][A] (M = Ag, Au; A = BF(4)(-), PF(6)(-), NO(3)(-)), prepared by coordination of the mesomorphic L = Hpz(2R(n)) or non-mesomorphic L = Hpz(R(n)) pyrazole ligands (Hpz(2R(n)) = 3,5-bis(4-alkyloxyphenyl)pyrazole; Hpz(R(n)) = 3-(4-alkyloxyphenyl)pyrazole), has been studied. The complexes exhibit enantiotropic behaviour, showing smectic A (SmA) mesophases. The choice of the ligands allows the achievement of 'H' or 'U' molecular shapes, which appear to be responsible for the attainment of liquid crystal mesophases, these not being dependent on the coordinating or non-coordinating nature of the A counteranions. The new complexes are photoluminescent both in the solid state and in solution at room temperature. In addition, the luminescent behaviour of selected compounds as a function of the temperature indicates that the luminescence is maintained in the mesophase.

Pyrazole Complexes and Supramolecular Chemistry

“…The new compounds were found to display luminescence both in solution and in the mesophase. [51] Lodeiro, Cano et al prepared a number of [M(pyrazole) 2 ]-X (M = Ag, Au; X = anion) salts and observed hydrogen bonding between the ligated pyrazoles and the anion in the solid state (Figure 19), metallotropy in solution, mesomorphism, and luminescent behavior in solution and, for some compounds, in the mesophase. [51] Figure 19.…”

Gold Liquid Crystals in the XXI Century

“…Therefore, very subtle changes can inhibit the mesomorphism. ) has been prepared by coordination of the mesomorphic 3,5-bis(4-alkyloxyphenyl)pyrazole or non-mesomorphic 3-(4-alkyloxyphenyl)pyrazole ( Figure 24) [40]. The complexes show smectic A mesophases, independently of the anion.…”

Luminescence and crystal structure of 2,2-difluoro-4-(9-anthracyl)-6-methyl-1,3,2-dioxaborine

“…Unlike respective 1,3-dicarbonyl compounds, boron b-difluoride diketonates produce an intensive luminescence in both solutions and crystals [1,2]. Recently, a substantial increase of interest has been observed to regard to new methods of synthesis [3,4] and optical and photophysical properties [5][6][7] of this class of compounds.…”