Aggregation and Tunable Color Emission Behaviors of l‐Glutamine‐Derived Platinum(II) Bipyridine Complexes by Hydrogen‐Bonding, π–π Stacking and Metal–Metal Interactions

Abstract

An l‐glutamine‐derived functional group was introduced to the bis(arylalkynyl)platinum(II) bipyridine complexes 1–4. The emission could be switched between the 3MLCT excited state and the triplet excimeric state through solvent or temperature changes, which is attributed to the formation and disruption of hydrogen‐bonding, π–π stacking, and metal–metal interactions. Different architectures with various morphologies, such as honeycomb nanostructures and nanospheres, were formed upon solvent variations, and these changes were accompanied by 1H NMR and distinct emission changes. Additionally, yellow and red emissive metallogels were formed at room temperature due to the different aggregation behaviors introduced by the substituent groups on bipyridine. The thermoresponsive metallogel showed emission behavior with tunable colors by controlling the temperature. The negative Gibbs free‐energy change (ΔG) and the large association constant for excimer formation have suggested that the molecules undergo aggregation through hydrogen‐bonding, π–π, and metal–metal interactions, resulting in triplet excimeric emission.

Tuning energy landscapes and metal–metal interactions in supramolecular polymers regulated by coordination geometry

“… 39,40 Particularly, in contrast to discrete supramolecular systems such as helicates, 41,42 catenanes 43,44 or cages, 45,46 the coordination geometry is often underappreciated in the context of metallosupramolecular polymerization. While there are countless studies utilizing mono-, 47–49 bi-, 50–52 and tridentate 53–55 ligands, the effect of changing the ligand system is typically excluded from discussion and often consequential differences in molecular design render such comparisons unfeasible. Moreover, a simple coordination geometry change ( cis -/ trans -isomerism) is difficult to investigate due to the rapid interconversion between both species in solution.…”

Modulation of Metallophilic and π–π Interactions in Platinum Cyclometalated Luminophores with Halogen Bonding

“…The low energy emission due to the formation of excimers has been utilized for the fabrication of white and near‐IR electroluminescent devices [6] . The relative weakness of these secondary contacts determines the sensitivity of Pt II ‐based molecular materials to external stimuli (mechanical, thermal, chemical), which cause distinct optical responses [5c, 7] …”

Thermo-responsive light-emitting metal complexes and related materials

“…In addition to the thermal-activated non-radiative decay, many other factors may be activated or influenced by temperature, including the effective molecular conformation or configuration transformation of flexible systems, 61,62 the degree of inter-or intramolecular π-π stacking and metal-metal interactions existing in aggregates or clusters of Rh(I), Pt(II), Cu(I), Ag(I), and Au(I) complexes, 39,[63][64][65] the dynamic association or dissociation process of metal and lanthanide complexes, 66,67 phase transition, [68][69][70][71] the degree of inter-or intramolecular energy transfer of donor/acceptor systems, 72,73 as well as the thermal equilibrium of different excited states. 74,75 These mechanisms will be discussed in more detail in specific examples in the following chapters.…”

“…[1][2][3][4] In particular, thermo-responsive functional materials with specific luminescence changes have attracted wide attention due to their potential applications in temperature sensing, [5][6][7][8][9][10][11][12] biological imaging, [13][14][15][16][17][18][19][20] optoelectronic devices, [21][22][23][24][25] and information processing. [26][27][28] To date, tremendous progress has been made in the development of thermo-responsive light-emitting materials, including various organic dyes and polymers, [29][30][31][32][33][34][35][36][37] metal complexes, [38][39][40][41][42][43][44] metal clusters and metal-organic frameworks (MOFs), [45][46][47][48]…”