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, 11 (1), 408

Insulated Conjugated Bimetallopolymer With Sigmoidal Response by Dual Self-Controlling System as a Biomimetic Material

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Insulated Conjugated Bimetallopolymer With Sigmoidal Response by Dual Self-Controlling System as a Biomimetic Material

Hiroshi Masai et al. Nat Commun.

Abstract

Biological systems are known to spontaneously adjust the functioning of neurotransmitters, ion channels, and the immune system, being promoted or regulated through allosteric effects or inhibitors, affording non-linear responses to external stimuli. Here we report that an insulated conjugated bimetallopolymer, in which Ru(II) and Pt(II) complexes are mutually connected with insulated conjugations, exhibits phosphorescence in response to CO gas. The net profile corresponds to a sigmoidal response with a dual self-controlling system, where drastic changes were exhibited at two threshold concentrations. The first threshold for activation of the system is triggered by the depolymerization of the non-radiative conjugated polymer to luminescent monomers, while the second one for regulation is triggered by the switch in the rate-determining step of the Ru complex. Such a molecular design with cooperative multiple transition metals would provide routes for the development of higher-ordered artificial molecular systems bearing bioinspired responses with autonomous modulation.

Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Conceptual illustration of sigmoidal response by dual self-controlling system.
a Modulator in the relay of biological information. b Chemical responses for the target concentration in conventional responses. c Dual self-controlling responses (this work) (S: substrate, T: target, and P: product). d Schematic strategies for self-activation based on random depolymerization. e Self-regulation based on a switch in the rate-determining step (c1 and c2 are the threshold concentrations).
Fig. 2
Fig. 2. Synthesis and response of bimetallopolymer.
a Illustrations of the phosphorescence sensing mechanism based on a conjugated bimetallopolymer with two transition metals. b The synthetic route to the insulated conjugated bimetallopolymer 6.
Fig. 3
Fig. 3. Optical analyses of Pt complexes and bimetallopolymer.
a Emission spectra of Pt complexes 4 and in deoxygenated toluene (concentration: 10−5 M). The spectra were corrected to the same number of photons absorbed at the excitation wavelength. b SEC profiles at various time points (blue: 0 min, green: 5 min, and orange: 20 min). c Photographic images upon excitation at 365 nm, and d emission spectra at a concentration of 10−2 mg/mL in deoxygenated toluene under excitation at 365 nm after depolymerization of the bimetallopolymer 6 with CO gas at various time points. e Photographic images and f emission intensities under deoxygenated conditions after depolymerization of the bimetallopolymer 6 with various gases under UV irradiation. a1% (v/v) H2S was present in the N2 gas.
Fig. 4
Fig. 4. Optical output with the dual self-controlling system.
a SEC profiles (UV detector, 380 nm) and b concentration dependence of the emission intensities at 557 nm (deoxygenated condition, excitation at 365 nm) after reaction at 100 °C for 10 min with various concentrations of CO gas. c Ligand substitution reaction of the Ru(TTP)(L)Py complex with CO (Py: pyridine, L: ligand).
Fig. 5
Fig. 5. Summary of the depolymerization steps with two thresholds.
a Change in the optical intensity with increasing target concentrations. b The design principle for self-activation and self-regulation ([M]: concentration of sensing metal, [T]: target concentration, k and k′ reaction rate constants).
Fig. 6
Fig. 6. Tunable thresholds in dual self-controlling system.
Concentration dependence of the emission intensities at 557 nm (deoxygenated condition, excitation at 365 nm) after reactions with various concentrations of CO gas; a at 100 °C for 3 min and b at 90 °C for 10 min.

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