Synthesis and Photophysical Properties of Self‐Assembled Metallogels of Platinum(II) Acetylide Complexes with Elaborate Long‐Chain Pyridine‐2,6‐Dicarboxamides

Abstract

A series of platinum(II) acetylide complexes with elaborate long-chain pyridine-2,6-dicarboxamides was synthesized. These metal complexes are capable of immobilizing organic solvents to form luminescent metallogels through a combination of intermolecular hydrogen bonding, aromatic π-π, and van der Waals interactions. Fibrillar morphologies were identified by TEM for these metallogels. Unique photophysical properties associated with the sol-to-gel transition have been disclosed with luminescence enhancement at elevated temperatures, which is in sharp contrast to typical thermotropic organogels or metallogels reported in the literature. Such unusual luminescence enhancement is attributed to the increased degree of freedom at higher temperatures that results in the formation of favorable molecular aggregates in the excited state through enhanced aromatic π-π and metallophilic Pt(II)···Pt(II) interactions. Structurally similar Pt-bp3 is not able to gel any common organic solvents. The inability of Pt-bp3 to form gels illustrates the importance of gelation to the macroscopic photophysical properties; Pt-bp3 does not show emission enhancement at elevated temperatures due to its low tendency to form strong aggregates in the ground state.

Control over the Self‐Assembly Modes of PtII Complexes by Alkyl Chain Variation: From Slipped to Parallel π‐Stacks

“…[21][22][23][24][25][26][27][28][29][30] These systems have a strong propensity to aggregate in solution and in the solid state via Pt•••Pt and/or other secondary forces, as recently shown for various classes of complexes in a comprehensive review by Yam and co-workers. 31 Among them, the self-assembly features of hydrophobic Pt(II) complexes with acetylide, [32][33][34][35][36] bidentate, [37][38][39] tridentate N-donor, [40][41][42] and cyclometalating ligands [43][44][45] are relatively well understood. 31 In contrast, their hydrophobic counterparts featuring non-chelating ligands and, in particular, bis(pyridyl) Pt(II) complexes have been limited to liquid crystalline materials [46][47][48] and hydrogen-bonded metallogelators.…”

Bright, Multi‐responsive, Sky‐Blue Platinum(II) Phosphors Based on a Tetradentate Chelating Framework

“…[5] Because excimer formation is ab imolecular and diffusion controlled process,e xcimer emission is highly dependent on temperature and often on pressure as well, [5] and could be controlled effectively by adjusting the strength of the molecular interactions or their medium. [1c, 7, 8] Although an umber of Pt II complexes have been reported to display temperature (T), [9] pressure (P) [1c, 4c, 8b] or lightdependent [1c] excimer emission, they either have al ow emission quantum efficiency or poor stability in the excited state,thus greatly limiting their practical applications.Infact, bright, multi-stimuli responsive systems based transitionmetal phosphorescent excimers remain elusive.W ea nd others have shown that fully constraining the geometry of the Pt II center with tetradentate chelating ligands disfavors tetrahedral distortion in the excited state,giving dramatically increased phosphorescent efficiencies and photostability to the metal complexes [10] which lead to highly robust blue/deep blue Pt II phosphors for high efficiency blue OLEDs. [6c] Excimers based on metal complexes have unique advantages in applications because of their ability to access long-lived phosphorescent states.S quareplanar Pt II complexes are most prevalent among transitionmetal complexes in producing excimers because of their flat geometry and have been successfully utilized in achieving white light or NIR organic light-emitting diodes (OLEDs) and data storage devices based on this principle.…”

Luminescent Amphiphilic 2,6‐Bis(1,2,3‐triazol‐4‐yl)pyridinePlatinum(II) Complexes: Synthesis, Characterization, Electrochemical, Photophysical, and Langmuir–Blodgett Film‐Formation Studies

“…The procedure was similar to that for complex 9, except that 4-ethynyl-N,N-dimethylaniline (73 mg, 0.50 mmol) was used in place of phenylacetylene. Yield: 53 mg (19 %); 1 H NMR (300 MHz, CD 3 CN, 298 K, relative to SiMe 4 ): d = 2.92 (s, 6 H; -NA C H T U N G T R E N N U N G (CH 3 ) 2 ), 5.76 (s, 4 H; -CH 2 -), 6.69 (d,J = 8.8 Hz,2 H;7.17 (d,J = 8.8 Hz,2 H;10 H;7.95 (d,J = 8.0 Hz,2 H;pyridine),8.28 (t,J = 8. CN: C 41.95,H 3.38,N 12.07;found: C 41.96,H 3.19,N 12.01.…”

“…After removal of solvent from the filtrate, the desired product was obtained as a yellow solid. Yield: 86 mg (27 %); 1 H NMR (400 MHz, CDCl 3 , 298 K, relative to SiMe 4 ): d = 0.69 (s, 3 H; cholesteryl proton), 0.86-0.88 (m, 6 H; cholesteryl proton), 0.92 (d,J = 6.4 Hz,3 H;cholesteryl proton), 0.97 (t, J = 7.3 Hz, 6 H; -CH 3 ), 0.95-1.52 (m, 28 H; -CH 2 -, cholesteryl proton), 9 H;cholesteryl proton),2 H;cholesteryl proton),5 H; C 50.88, H 6.23, N 8.65; found: C 50.45, H 6.14, N 8.27.…”

“…The procedure was similar to that for complex 14, except that complex 2 (146 mg, 0.18 mmol) was used in place of complex 1. Yield: 53 mg (23 %); 1 H NMR (400 MHz, CDCl 3 , 298 K, relative to SiMe 4 ): d = 0.69 (s, 3 H; cholesteryl proton), 0.84-0.88 (m, 12 H; -CH 3 , cholesteryl proton), 0.92 (d,J = 6.5 Hz,3 H;cholesteryl proton),44 H; -(CH 2 ) 5 -, cholesteryl proton), 9 H;cholesteryl proton),2 H;cholesteryl proton),1 H; H 7.41, N 7.13; found: C 54.68, H 7.24, N 6.98.…”