An overview of phosphorescent metallomesogens based on platinum and iridium

Abstract

Metallomesogens – liquid crystals containing metal centers – have attracted much interest owing to their interesting magnetic and electro-optical properties. Due to the theoretical 100% internal quantum efficiency, here, a brief overview of recent research on platinum/iridium-based metallomesogens including their molecular design and structure-property relationships is reported.

Liquid crystalline copper(i) complexes with bright room temperature phosphorescence

“…4 In the last two decades, the field of luminescent liquid crystalline metal complexes, a particular class of metallomesogens, 5 has developed significantly. [6][7][8] The liquid crystal state offers interesting properties such as the control of the organization and anisotropy combined with better solubility and processing. 9 Indeed, a controlled orientation of phosphorescent molecules in active layers has become a crucial topic to improve solid-state emission and efficiency in electronic devices.…”

“…However, the study of the efficiency (quantum yield) in the liquid crystal phase has been largely overlooked. 7 Nowadays, the goal of attaining low temperature liquid crystals with high emission efficiencies in the liquid crystalline state is fostering the search for new molecules.…”

Playing with PtII and ZnII Coordination to Obtain Luminescent Metallomesogens

“…Luminescent d-block metallomesogens are promising functional materials for practicala pplications.T hey have mainly been investigated in terms of obtaining polarised emission to be used as backlighting in displays, [1][2][3][4] but also some studies concerning their use as stimuli responsive materials for sensing [5,6] or security inks, [7] or high-hole mobility materials for electroluminescent devices [8] have been reported.D espite recentp rogress with square-planar Pt II and octahedral Ir III complexes, which are considered among the best emitters, there is still considerable work to be done to control the phase type and transition temperatures or to improvet he luminescence in the mesophase. [9] In fact, only af ew studies on the mesophases of luminescent liquid-crystalline transition metal complexes have been carried out, with, just to cite non-exhaustively,t he contributions of Bruce et al on Ir III , [8,[10][11][12] Espinet et al [13] and Tsutsumi et al [14,15] on Au I ,G imenØnez et al on Ag I [16] and Zn II , [17] Cârcu et al on Pd II , [18][19][20] Cano et al on Ag I [21][22] and Pucci, Crispini and Ghedini et al on Ru II , [23] Ag I , [24][25][26] Ir III [27] and Zn II [28,29] complexes. For practical applications,t echnological and economic issueshave to be taken into account,such as thermaland optical stabilities, availability and cost of the precursors and straightforward syntheses.…”

Blue Electrofluorescence Resulting from Exergonic Harvesting of Triplet Excitons

“…The major breakthroughs in the development of organic light‐emitting devices (OLEDs) have been provided by the discoveries of novel exciton‐harvesting materials. The most successful examples are room‐temperature phosphorescent complexes of late transition metals such as Ir(III) or Pt(II) . The complexes are capable of producing highly efficient electrophosphorescence by harvesting all the electronically generated excitons through fast intersystem crossing (ISC) provided by large spin–orbit coupling (SOC) ( Figure a).…”