Understanding M–ligand bonding and mer-/fac-isomerism in tris(8-hydroxyquinolinate) metallic complexes

Abstract

Tris(8-hydroxyquinolinate) metallic complexes, Mq3, are one of the most important classes of organic semiconductor materials. Herein, the nature of the chemical bond in Mq3 complexes and its implications on their molecular properties were investigated by a combined experimental and computational approach. Various Mq3 complexes, resulting from the alteration of the metal and substitution of the 8-hydroxyquinoline ligand in different positions, were prepared. The mer-/fac-isomerism in Mq3 was explored by FTIR and NMR spectroscopy, evidencing that, irrespective of the substituent, mer-and fac-are the most stable molecular configurations of Al(III) and In(III) complexes, respectively. The relative M-ligand bond dissociation energies were evaluated experimentally by electrospray ionization tandem mass spectrometry (ESI-MS-MS), showing a non-monotonous variation along the group (Al > In > Ga). The results reveal a strong covalent character in M-ligand bonding, which allows for through-ligand electron delocalization, and explain the preferred molecular structures of Mq3 complexes as resulting from the interplay between bonding and steric factors.The mer-isomer reduces intraligand repulsions, being preferred for smaller metals, while the fac-isomer is favoured for larger metals where stronger covalent M-ligand bonds can be formed due to more extensive through-ligand conjugation mediated by metal ''d'' orbitals.

Heteroassembly Ability of Dicationic Ionic Liquids and Neutral Active Pharmaceutical Ingredients

“…The E cm,1/2 can be used to measure the relative dissociation energy, in addition to being a well-established research strategy regarding the relative binding energies/stabilities of several systems. 35,37,38 The E cm,1/2 observed for the [BisOct(MIM)X] + species is shown in Table 2.…”

8-Hydroxyquinoline complexes (Alq3) on Al(111): atomic scale structure, energetics and charge distribution

“…When three molecules are complexed to the Al atom, the Alq mer 3 isomer is found to be the most stable one by 120 meV, ‡ close to the value of 210 meV calculated by Lima et al (M06-2X/6-31+G(d,p)/SDD level of theory). 3 High electrons transfers are observed from the Al atom to the molecules upon complexation with two oxidation states of the Al atom in the systems (Al I in Alq and Al III in Alq 2 and Alq 3 ). It leads to a strong bonding between the Al atom and the q molecules.…”

“…and experimental2,3,55 studies. The shorter bond lengths in the Alq 2 species, which has a symmetric structure, show stronger O-Al and N-Al interactions than in the other Alq n species.…”

Synthesis, Characterization and Antibacterial Properties of Nickel(II) Complex with 4-Aminoantipyrine Ligand

“…5). The complex is the most Therefore, such coordination avoided the reduction in electron delocalization and also contributed to a stronger M-ligand bond [27].…”