K⁺, Sr²⁺-Triggered Phase Transitions from Chiral Thermotropic Liquid Crystalline to G-Quadruplex CTLC with Circularly Polarized Luminescence

Abstract

A convenient method to prepare luminescently thermotropic liquid crystalline (TLC) with chiral centers is established by combining cationic Gemini surfactants, C n H2n+1(CH3)2N+(CH2)2N+(CH3)2C n H2n+1·Br2 (n–2–n·2Br, n = 10, 12, 14, and 16, respectively) and guanosine 5′-monophosphate disodium salt (GMP). Under thermally annealing, the complexes of surfactant-GMP (n-GMP) self-assemble into TLCs with circularly polarized luminescence (CPL) performance, except for 10-GMP. The phase structure and CPL handedness in TLCs can be regulated by changing the alkyl chain length of n–2–n·2Br. Columnar tetragonal (Colt) mesophase of 12-GMP exhibits right-handed CPL (R-CPL) emission, while chiral smectic C (SmC*) phases containing 14- or 16-GMP display left-handed CPL (L-CPL) emission. The introduction of K+ or Sr2+ triggers n-GMP to be G-quadruplexes with identical chirality and luminescence, and further regulates the phase structure and CPL property. TLCs can be transformed to be columnar rectangular (Colr) or Colt phases with R-CPL emission. We find that the mesogenic units feature the same chiral moiety can realize R- and L-CPL emitting, and prepare the tunable CPL-active LCs through natural biomolecules. These results deepen our understanding of chiral luminescence mesogens and G-quadruplex structures, providing the new insight for the fabrication of nondoped LC materials with CPL performance.

Ionic liquid crystals based on amino acids and gemini surfactants: tunable phase structure, circularly polarized luminescence and emission color

“…30 In our previous work, chiral thermotropic LCs consisting of a guanosine derivative and cationic gemini surfactant showed controllable CPL handedness. 31 Besides, the majority of current CPL-active LCs have a monotonous emission color. Considering the desirable role of multicolor emission in display technology, 32,33 the construction of CPL ILCs with color-tunable fluorescent behavior will be feasible for practical applications.…”

Guanine Analogue-Based Assemblies: Construction and Luminescence Functions

“…Commun . ), (b 2 ) G-quadruplex ionogels (reproduced with permission from ref ; copyright 2021, Colloids Surf., A ), and (b 3 ) GMP-based chiral thermotropic liquid crystals (CTLC) (reproduced from ref ; copyright 2021, American Chemical Society). (c 1 ) Representative chemiluminescent assemblies (reproduced with permission from ref ; copyright 2021, Chem.…”

“…Recently, the nondoping fluorescent G-based assemblies have been well explored, such as GMP-based carbon dots, G-quadruplex ionogels with adjustable chirality, and GMP-based chiral thermotropic liquid crystals (CTLC), as shown in Figure b 1 –b 3 . − In ionic liquid ethylammonium nitrate (EAN), the photoluminescence property of the purine chromophore was preserved and the forming G-quadruplex independently delivered the expected CPL, which was exactly distinct from the performance in aqueous solution. ,, By the impact of water, the fluorescence of the chromophore in aqueous solution was quenched at a lower concentration and did not appear until reaching a higher concentration . This phenomenon implies the clustering-triggered emission (CTE) of the guanine molecules.…”

“…CTE refers to the visible emission of nonconventional chromophores containing π and n (lone pair) electrons after surviving the clustering, electron cloud overlapping, extended electron delocalization, and conformation rigidifcation . Therefore, the GMP-surfactant-based complexes or CTLC after self-aggregation showed evident fluorescence in the solvent-free environment . With the triggering of K + or Sr 2+ , the CPL of CTLC could switch between L-CPL and R-CPL.…”

“…38 Therefore, the GMP-surfactant-based complexes or CTLC after self-aggregation showed evident fluorescence in the solvent-free environment. 36 With the triggering of K + or Sr 2+ , the CPL of CTLC could switch between L-CPL and R-CPL. These phenomena have suggested their CTE possibility, although there is no theoretical calculation to certify the CTE mechanism of guanine derivatives.…”