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Phosphorescence properties and bioimaging of pyridine auxiliary ligand cyclometalated Pt(II) complex with multiphoton absorption
*Corresponding author: E-mail address: cacfrw@126.com (J. Yang)
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Received: ,
Accepted: ,
Abstract
We synthesized the cyclometalated Pt(II) complex (Pt-Lyb) modified by a pyridine auxiliary ligand with electron delocalization capability. The introduction of pyridine ethylene ligand increases the conjugate structure of the system, and the heavy atom effect of the Pt(II) complex can effectively promote the intersystem crossing (ISC) between the singlet and triplet states of the Pt(II) complex. Viscosity test results revealed that the two-photon and three-photon absorption activities were enhanced with the increase in viscosity. Besides, it was found that Pt-Lyb had a better inhibitory effect on cancer cells and a stronger ability to target subcellular organelles (cell membranes) than cisplatin. This indicates that the platinum complexes have potential application prospects in bioimaging.
Keywords
Bioimaging
Multiphoton absorption
Pyridine auxiliary coligands
Pt(II) complexes
1. Introduction
Phosphorescence is a kind of light-cooling luminescence phenomenon that gives off light slowly, whose luminescence persists. Compared with fluorescence, phosphorescence has a longer excited state lifetime. At present, the common phosphorescent materials include organic phosphorescent materials, inorganic phosphorescent materials, and organic-inorganic hybrid materials [1-7]. However, Pt(II) complexes are used widely as post-transition metal complexes because of heavy atom effects with strong spin-orbit coupling (SOC), rapid intersystem crossing (ISC), and triplet emission via SOC [8-11]. Therefore, it often exhibits phosphorescent emission behavior at room temperature.
Viscosity is an important microenvironmental parameter, and it has a wide range of applications in biological probes [12-14]. Many complex molecules have a lot of sigma bonds; these sigma bonds will rotate freely in the solvent and consume the energy of the molecular excited state, resulting in quenched or weak molecular emission. In high-viscosity solutions, the energy consumed by non-radiative transitions of molecules is reduced due to the limitation of intramolecular rotations by the surrounding viscosity, resulting in enhanced transport [15,16].
Many transition metal complexes with nonlinear optical (NLO) properties have been investigated; the Pt(II) complex is particularly important because of its unique structure, excellent NLO response, and light-limiting application prospects [17-20]. The heavy atomic effect of Pt(II) ions can effectively promote the spin-orbital coupling of molecules, enhance the absorption of spin resistance transition from singlet state (S0) to triplet state (T1), and improve the efficiency of ISC [21]. This stable triplet state facilitates the desaturation of the excited state. Some complexes based on Pt(N^N^C) or Pt(N^N^N) have been shown to have some NLO properties [22-24]. However, most of them have defects such as poor molecular stability, small NLO effect, and short absorption and emission wavelength. Therefore, designing platinum (II) complexes with high stability and a large NLO effect is a challenging task.
In this study, the β-N, N-dibutyl tripyridine Pt(II) complex was selected as the matrix from the perspective of synthesis yield and solubility. To extend the complex conjugation system and adjust the molecular luminescence angle, we chose D-π-A vinylpyridine derivatives as co-ligands (Lyb). The novel cyclometalated Pt(II) complex (Pt-Lyb) was synthesized. Through a systematic study of its photophysical properties, the triaxial emission behavior of the complex was studied by theoretical calculation and phosphorescent experiment. The NLO properties of complexes were studied in detail. Cytotoxic combined confocal imaging was performed to explore the anticancer activity of the complex [25].
Modified pyridine auxiliary coligands with electron delocalization based on N, N-dibutyl terpyridine Pt(II) complex, the cyclometalated Pt(II) complex was synthesized [26]. The addition of the pyridine ethylene ligand increases the conjugated structure of the system. The heavy atom effect of Pt(II) can effectively promote the transition between singlet and triplet systems.
Based on the β-N, N-dibutyl tripyridine Pt(II) complex, it reacted with the pyridine ethylene ligand by forming Pt-N bonds. Finally, we obtained the C^N^C ring metal Pt(II) complex. The introduction of the pyridine ethylene ligand increases the conjugate structure of the complex. By steady-state phosphorescence and transient emission spectra, the triplet-state phosphorescent emission properties of the complex were verified. In multiphoton absorption experiments, it was found that the complex had strong absorption effects of two photons (800 nm) and three photons (1300 nm) in the near-infrared (NIR) region. It was found that the complex had better cytotoxic selectivity and subcellular organelle (cell membrane) targeting ability than cisplatin.
2. Materials and Methods
2.1. Reagents, instruments, and test methods
The solvents used were of pure analytical grade. Preparation for liquor: Pt-Lyb (0.0068g) was weighed and diluted with 5.0 mL of dimethyl sulfoxide (DMSO) and 10-3 M mother liquor was used. Steady-state phosphorescence test was carried out on a fully functional steady-state transient spectrometer FLUORMAX-4P consisting of 3 mL of 100 µM Pt-Lyb DMSO solution; The excitation wavelength was measured on 450 nm with a slit of 5 nm.
2.2. Synthesis of Pt-Lyb
Pt complex (0.10 g, 0.09 mmol), pyridine auxiliary ligand Lyb (0.03 g, 0.012 mmol), and 20 mL of refined methylene chloride were successively added to a 100 mL Schlenk flask, stirred for 48 h at room temperature. The reaction liquid slowly precipitated a yellow solid from a red transparent solution (Scheme 1). After completion of the reaction, the solvent was removed under reduced pressure, and the residue was filtered and washed. The residue was successively washed twice with 10 mL of methylene chloride and 10 mL of ethanol. Yellow powder solid Pt-Lyb was obtained by collecting filter residue (the synthetic yield of Pt-Lyb is 51.7%).
- The synthesis route of the complex Pt-Lyb.
3. Results and Discussion
3.1. Crystal structure
Crystals of ligand Lyb were obtained by the solvothermal method. An appropriate amount of compound was placed in a hard glass tube with 15 mL of methanol, and the temperature rose to 65°C. After the compound was fully dissolved, a yellow transparent needle crystal (Lyb) was obtained by programmed cooling. Crystal data were collected by a X-ray single crystal diffractometer, and OLEX2 software was used to analyze the crystal data. The crystal structure has been shown in Figure 1, related crystal parameters have been shown in Table 1, selected bond distances and angles have been shown in Table 2.
- Crystal structure of Lyb, all H atoms were omitted for clarity.
| Empirical formula | C136N16O8 |
|---|---|
| Formula weight | 248.13 |
| T[K] | 296(2) |
| Crystal system | monoclinic |
| Space group | P21/n |
| a[Å] | 9.656 |
| b[Å] | 30.415 |
| c[Å] | 10.072 |
| α[°] | 90 |
| β[°] | 100.75 |
| γ[°] | 90 |
| V/Å3 | 2906.1 |
| Z | 1 |
| Dcalcd/(g·cm−3) | 0.024 |
| F(000) | 21.0 |
| θ range | 11.638-139.86 |
| Reflections collected | 34569 |
| Independent reflections | 5432 |
| GOF on F2 | 1.068 |
| R1[I >2σ(I)] | 0.0525 |
| wR2[I >2σ(I)] | 0.2729 |
a, b, and c represent the lengths of the three edges of the unit cell, also known as lattice constants, representing the periodic distance along the crystallographic axis direction. While a complete geometric description of the unit cell also requires the angles. α, β, and γ between the three axes, where α is the angle between edges b and c, β is the angle between edges a and c, and γ is the angle between edges a and b. In crystallography. F2 (often written as F2) represents the diffraction intensity, which is the intensity value of the diffraction spot observed in X-ray single crystal diffraction experiments.
| Selected bonds | Value(Å) | Selected angles | (°) |
|---|---|---|---|
| O2 C21 | 1.428(4) | C22 N3 C20 | 122.1(3) |
| O1 C4 | 1.427(4) | C22 N3 C19 | 121.6(3) |
| N3 C22 | 1.376(5) | C20 N3 C19 | 116.2(3) |
| N3 C20 | 1.460(5) | C5 N2 C3 | 120.8(3) |
| N3 C19 | 1.468(5) | C5 N2 C2 | 121.9(3) |
| N2 C5 | 1.368(5) | C11C12C13 | 124.7(3) |
| N2 C3 | 1.473(4) | N2 C5 C6 | 121.0(3) |
| N2 C2 | 1.462(4) | N2 C5 C10 | 121.9(3) |
| N4 C33 | 1.353(5) | C10C5 C6 | 117.1(3) |
3.2. Crystal analysis of auxiliary ligands
In the crystal data at Lyb, the reliability of the crystal structure is R1= 0.0525, wR2 = 0.2729, and the goodness-of-fit on F2 (GOOF) value is 1.068. Crystal structure analysis shows that the compound belongs to the monoclinic crystal system, P21/n space group. In the crystal data of L3, the reliability of the crystal structure is R1 = 0.0578, wR2 = 0.2074, GOOF value is 1.038. Crystal structure analysis shows that the compound belongs to the monoclinic crystal system, P21/n space group.
As shown in Figure 2, at first, the dihedral angle between the electron-donating hydroxyethyl aniline plane and the electron-pulling pyridine ring plane is 4.39°, which is almost coplanar to facilitate electron flow. Secondly, the C-N single bond length between hydroxyethyl aniline and the benzene ring is 1.363Å. Between the normal C-N single bond (1.47Å) and the C=N double bond (1.28Å), it shows that the aniline group and benzene ring have a good p-π conjugate system, and the molecule has excellent stability. The bond length lies between that of a typical single and double bond; this kind of structure characteristic lays a good foundation for its NLO effect. In the crystal structure of Lyb, the intermolecular layer is mainly packed. The intermolecular force is a hydrogen bond interaction, and the intermolecular hydrogen bond interaction mode has been shown in Figure 2.
- The intramolecular angle between two planes and BLA in the crystal structure of Lyb.
3.3. Study on linear photophysical properties of complexes
The UV-absorbable spectrum of the complex was measured in the range of 200-700 nm, five solvents of different polarities were selected, and the effect of the solvent on the absorption spectrum of the complex was studied. The concentration of the measured samples was 10 μM, and a 1 cm cuvette was used for the test. The UV-Vis absorption spectra have been shown in Figure 3. It can be seen from Figure 3, the complex Pt-Lyb has two absorption peaks of moderate intensity in the range of 260-500 nm (The maximum absorption wavelength is located at 425-475 nm; ε∼10-4 mol/(cm·L)). The high energy absorption peak is ∼295 nm, C^N^C of the main structure 1IL [π(bzimpy)→π*(bzimpy)] process is accompanied by an entire intramolecular charge transfer (ICT) [π(bzimpy)→π*(bzimpy)]. The low-energy absorption peak at ∼450 nm belongs to the process of Pt complex 1MLCT[dπ(Pt)→π*(bzimpy)]. The absorption peak of 625 nm appeared in dichloromethane, which is due to the poor solubility in dichloromethane. There are π···π and Pt···Pt interactions between molecules. It should be attributed to the process of Pt···Pt to the ligand charge transfer 1MMLCT[dσ(Pt)→π*(bzimpy)]. The position of the low-energy absorption peak at 450 nm showed a certain degree of blue shift with increasing solvent polarity. These results indicate that the solvent molecules have a certain effect on the electron distribution of the transition orbitals of 1metal to ligand charge transfer (mlct) and 1ligand to ligand charge transfer (LLCT) complexes. The energy level difference between them will be changed. At first, with the introduction of the helper ligand, the absorption peaks showed a certain degree of blue shift (∼50 nm). Secondly, the maximum absorption peak of Pt-Lyb also gradually blue shifts with the increase of hydroxyethyl on the aniline group. This is because the ICT of the auxiliary ligand is enhanced with the increase of the electron donor group. When the 1MLCT of the Pt complex was weakened, the absorption spectrum was blue-shifted. It indicates that the auxiliary ligand has a certain influence on the absorption spectrum of the Pt(II) complex.
- UV-Vis absorption spectra of Pt-Lyb in different solvents (c = 10 μM).
3.4. Theoretical calculation
Time dependent-density functional theory calculation (TD-DFT) was used to further determine the charge transition of platinum complex, the theoretical calculation of the energy from the ground state of the singlet to the excited state of the singlet uses the sto-3g* basis set (C, O, H, N, S atom) and the Lanl2dz basis set (Pt atom). Figure 4 illustrates the specific energy levels of the frontier molecular orbitals, and Table 3 shows the main data about the energy level transitions.
- Molecular orbital energy diagrams for Pt-Lyb.
| Complex | Imax (nm) | Calculated E(eV) | Composition | Character |
|---|---|---|---|---|
| Pt-Lyb | 366.09 | 3.38 | (H-4→L+4)(0.03) | IL[π(auxiliary)-π(auxiliary)*] |
| 469.28 | 2.64 | (H-2→L+5)(0.05) | 1LMCT[dx2-y2(Pt)→π*] |
When the complex Pt-Lyb absorbed energy, charge transfer happened, which is charge transfer within the ligand[π(auxiliary) →π*(auxiliary)] /[π(C^N^C)-π(C^N^C)*]. The corresponding absorption wavelengths in the range of 460∼475 nm are consistent with the position of the short-wavelength absorption peak of the complex.
3.5. Steady state/transient emission spectra of complex
Pt(II)-Lyb complex belongs to a post-transition metal complex, which exhibits absorption spectra (Figure 5a) and emission spectra (Figure 5b), fluorescence emission (Figure 6), and phosphorescent emission behavior at room temperature. The phosphorescence was significantly red-shifted compared to the fluorescence, accompanied by a long radiation decay life (Figure 7a). Therefore, the steady-state phosphorescence emission behavior and transient phosphorescence emission lifetime of Pt-Lyb were studied.
- (a) Absorption and (b) emission spectra of Pt-Lyb with various concentration (1.0x10-5-1.0x10-4 mol L-1), respectively in DMSO.
- FL spectra for Pt-Lyb in different solvents.
- Radiation decay life and FL/PH spectra of Pt-Lyb: (a) radiation decay life; (b) FL/PH spectra; (c) PH spectra of 1 µs delay time.
At first, the FL spectra shown in Figure 7(b) were obtained by fluorescence and phosphorescent full collection modes. It can be found that Pt-Lyb has a fluorescence emission peak at 525 nm. However, a narrow emission peak appears around 575 nm. Therefore, in order to verify whether the new emission peak is a fluorescence peak or a phosphorescence peak, we set the delay time of the instrument to 1 µs. The phosphorescence spectrum shown on the right is obtained, and an obvious phosphorescence emission peak was found at 500 ∼700 nm for Pt-Lyb (Figure 7c).
3.6 Nonlinear optical properties of complex
3.6.1 Two-photon absorption properties of complex
Because Pt(II) complexes have two-photon fluorescence emission peaks, the two-photon absorption properties of the target Pt complexes, including the two-photon absorption coefficient and the size of the two-photon absorption cross section, have been determined by the open-aperture Z-scan technique. Figure 8 shows the open-hole fitting curve of the Pt(II) complexes. Table 4 lists the main two-photon absorption data for the Pt(II) complex. The reasons are as follows: Firstly, the C^N^C type main ligand has a good fluidity of π electrons in the molecule, and it has NLO properties; Secondly, metal Pt atoms can improve the electron flow of Pt(II) complex to enhance NLO response; Furthermore, the introduction of the auxiliary ligand with good NLO properties further enhances the NLO effect of Pt(II) complex. The above studies show that Pt(II) complexes are excellent NIR third-order NLO materials, which are expected to have potential applications in the field of biological imaging.
- The normalized open-aperture Z-scan transmittance of Pt-Lyb.
| Complex | λ/nm | β(cm·GW-1) | σ(GM) |
|---|---|---|---|
| Pt-Lyb | 800 | 2.420 | 99835±33 |
3.6.2 Three-photon absorption properties of complex
The three-photon absorption properties of Pt-Lyb were studied by the three-photon fluorescence contrast method. Because the Pt(II) complex has strong phosphorescence emission properties, it is necessary to select a cryogenic dish, and passing N2 (10 min) can remove the oxygen in the solution before the test. Three-photon phosphorescence emission spectra were obtained, three-photon absorption cross-section of the Pt(II) complex was calculated.
The three-photon phosphorescence maps of Pt-Lyb in the 1200∼1450 nm range were obtained using a multiphoton instrument with a spectral range of 450 nm to 625 nm. The spectral envelope is identical to the phosphorescence emission spectrum. Furthermore, the peak of Pt-Lyb was obtained under the excitation of a 1300 nm laser. We conducted three-photon verification experiments on Pt-Lyb, which proved that three-photon can induce the generation of phosphorescence. By varying the excitation optical power at the maximum excitation wavelength, input energy and output energy can be obtained. The results showed that there is a cubic relationship between the output energy and the input energy, and the slopes of the three complexes are all around 3 (Figure 9). Therefore, this experimental result also proves that the Pt(II) complexes have three-photon absorption properties. Pt-Lyb has a maximum three-photon absorption cross-section of 50 (10-81cm6s2photon-2) at the optimal excitation wavelength of 1300 nm (Figure 10). This means that the Pt(II) complex can be excited by 1300 nm NIR light and produce emission, which is further than the maximum absorption wavelength of the two-photon at 800 nm. Therefore, it has the potential to be developed as a three-photon phosphorescent probe for three-photon biological development.
- (a) Three-photon emission spectra (N2 atmosphere) and (b) verification of Pt-Lyb.
- Three-photon cross sections of Pt-Lyb in DMSO.
3.7. Viscosity response of complexes
3.7.1. Nonlinear optical properties when glycerol is added
Pt(II) complex has a lot of sigma bonds that can rotate freely, and they exhibit emission characteristics at room temperature, which respond to the viscosity of the solution. As shown in Figure 11, by adding glycerol to the PBS buffer, the solution viscosity was gradually increased by increasing the viscosity from 10% (glycerol content) to 90% (glycerol content). It can be found that the medium gradually increases with the viscosity of the solution. The FL emission intensities of Pt-Lyb were significantly enhanced, and the enhancement is around 45 times. The result indicates that Pt-Lyb can monitor environmental viscosity in real time and sensitively by FL spectrum. The responses of the phosphorescence spectrum to viscosity were further studied based on the phosphorescence emission properties of the Pt(II) complex.
- Changes in the FL spectra of Pt-Lyb at different glycerol concentrations.
The two-photon absorption cross section is an important property of two-photon fluorescent materials. As can be seen in Figure 12, the effective two-photon absorption cross-sections of Pt-Lyb increase obviously with the increase of solution viscosity. For example, the effective two-photon absorption cross-section of Pt-Lyb at 800 nm increased from 16 GM (30% glycerol) to 46 GM (90% glycerol), which is a nearly threefold increase. It shows that the two-photon absorption properties of Pt-Lyb have a very obvious response to the solution viscosity. Therefore, the advantages of two-photon microscopic imaging technology can be combined, and the viscosity in the body of the organism can be tested. It shows that the three-photon absorption properties of Pt-Lyb also have a very pronounced response to the solution viscosity. Therefore, the advantages of multiphoton microscopic imaging technology can be combined to measure the viscosity of the organism.
- (a) Two-photon and (b) three-photon absorption cross sections of Pt-Lyb at different glycerol concentrations.
3.8. Biodevelopment and anticancer activity study
It is well known that platinum molecules are highly effective in the field of anticancer. Platinum molecules with luminescent and anticancer activities are of great interest to chemical researchers [27-32]. The anticancer activity of C^N^C cyclometallic Pt(II) complexes was investigated on the basis of the detailed study of the photophysical properties of three Pt(II) complexes.
3.8.1. Cytotoxicity test
MTT assay was used to determine the effect of Pt(II) complex on tumor cells, HeLa (the human HeLa cells), and the inhibition of HELF (Human Embryonic Lung Fibroblasts) in normal cells was studied. Table 5 shows the IC50 of Pt(II) complexes for cancer and normal cells. To research the targeting of the complex to the suborganelle, we selected HeLa cells, used commercial dye on lysosome suborganelles (Cell Mask-tracker), and performed colocalization experiments with Pt-Lyb, which were carried out away from light. The experimental results have been shown in Figure 13.
| Compound | HeLa cells | HELF cells |
|---|---|---|
| Pt-Lyb | 7.5 ± 0.4 | 33 ± 2.3 |
| Cisplatin | 12.7 ± 0.8 | 16 ± 1.9 |
- Bioimages of Pt-Lyb (incubated with 10 μM/30 min at 37°C).
3.8.2. Cell development
Table 5 shows that the IC50 of Pt-Lyb on cancer cells and normal cells, the anticancer activity of the complex against HeLa was higher than that of cisplatin (7.1 µM∼7.5 µM). On the other hand, they do less damage to normal cells than cisplatin (32 µM∼36 µM). Therefore, these Pt(II) complexes have better anticancer application prospects than traditional cisplatin anticancer drugs and lay the foundation for subsequent cell imaging. The subcellular organelle targeting ability of the complexes was investigated on the basis of cytotoxicity. HeLa cells were incubated for 10 min at 37°C by adding 10 μM of Pt(II) complexes, and development images were taken under a confocal microscope. Cell Mask-tracker and Pt-Lyb were used for the colocalization tracking experiment. From Figure 13, we can see that the green signal of the Pt(II) complex overlaps well with the red signal of the commercial stain to form a yellow signal, which suggests that the complex could enter the cell membrane of HeLa cells within a short time.
4. Conclusions
Based on β-site N, N-dibutyl terpyridyl Pt(II) complex, it reacts with a pyridine auxiliary ligand by forming a Pt-N bond. The C^N^C type cyclometalated Pt(II) complex was obtained. The introduction of pyridine ethylene ligand increases the conjugate structure of the complex. The triplet phosphorescence emission properties of the complex were verified through steady-state phosphorescence and transient emission spectroscopy. Multiphoton absorption experiments show that Pt(II) complexes have strong two-photon (800 nm) and three-photon (1300 nm) absorption effects in the NIR region. Viscosity test results revealed that Pt(II) complexes can respond significantly to the solvent viscosity. At the same time, the two-photon and three-photon absorption activities were enhanced with the increase in viscosity. Based on the above experiments, it was found that Pt-Lyb had a better inhibitory effect on cancer cells and a stronger ability to target subcellular organelles (cell membranes) than cisplatin. This indicates that the platinum complexes have potential application prospects in bioimaging.
Acknowledgments
Thanks to the financial support from the National Natural Science Foundation of China (21275006, 21271004, 51432001 and 51372003), the Department of Education of Anhui Province (2024AH051239), the Project of Bengbu Medical University (2021BYZD013), and the Key Natural Science Research Foundation for University of Anhui (2022AH051442).
CRediT authorship contribution statement
Youlin Si: Conceptualization, Data Curation, Investigation, Writing-Original Draft, Funding acquisition. Jing Hu: Methodology, Software, Writing-Original Draft, Funding acquisition. Chengkai Zhang: Methodology. Zhi Cao: Data Curation, Software, Visualization. Ebeydulla Rahman: Resources, Visualization, Software. Yupeng Tian: Methodology, Supervision, Project administration, Validation, Funding acquisition. Junsong Yang: Methodology, Supervision, Validation, Project administration, Writing-Review & Editing, Funding acquisition.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Declaration of generative AI and AI-assisted technologies in the writing process
The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.
References
- New members of a class of cyclometalated 1,3-di-(2-pyridyl)benzene platinum(II) complexes bearing a tetrazole-thiolate ancillary ligand. Inorganica Chimica Acta. 2023;550:121446. https://doi.org/10.1016/j.ica.2023.121446.
- [Google Scholar]
- Color-tunable ultralong organic room temperature phosphorescence from a multicomponent copolymer. Nature Communications. 2020;11:944. https://doi.org/10.1038/s41467-020-14792-1.
- [Google Scholar]
- Carbon dots with dual-emissive, robust, and aggregation-induced room-temperature phosphorescence characteristics. Angewandte Chemie. 2020;59:1263-1269. https://doi.org/10.1002/anie.201911342.
- [Google Scholar]
- Two-coordinate copper(I)/NHC complexes: Dual emission properties and ultralong room-temperature phosphorescence. Angewandte Chemie International Edition. 2020;59:8210-8217. https://doi.org/10.1002/anie.201916379.
- [Google Scholar]
- Achieving high-performance solution-processed orange OLEDs with the phosphorescent cyclometallated trinuclear Pt(II) complex. ACS Applied Materials & Interfaces. 2018;10:10227-10235. https://doi.org/10.1021/acsami.7b18330.
- [Google Scholar]
- Long wavelength–emissive Ru(II) metallacycle–based photosensitizer assisting in vivo bacterial diagnosis and antibacterial treatment. . Proceedings of the National Academy of Sciences of the United States of America,. 2022.;119:e2209904119. https://doi.org/10.1073/pnas.2209904119.
- [Google Scholar]
- Construction of a 980 nm laser-activated Pt(II) metallacycle nanosystem for efficient and safe photo-induced bacteria sterilization. Science China-Chemistry. 2023;66:155-163. https://doi.org/10.1007/s11426-022-1440-2.
- [Google Scholar]
- The intriguing effect of thiolates as co-ligands in platinum(II) complexes bearing a cyclometalated 1,3-di(2-pyridyl)benzene. Inorganica Chimica Acta. 2022;532:120744. https://doi.org/10.1016/j.ica.2021.120744.
- [Google Scholar]
- Delocalization of excited state and emission spectrum of platinum(II) bipyridine complex in crystal: Periodic QM/MM study. The Journal of Physical Chemistry C. 2020;124:10453-10461. https://doi.org/10.1021/acs.jpcc.9b11559.
- [Google Scholar]
- An efficient Heterodinuclear Ir(III)/Pt(II) complex: Synthesis, photophysics and application in light-emitting electrochemical cells. Journal of Materials Chemistry C. 2019;7:10672-10682. https://doi.org/10.1039/C9TC02930C.
- [Google Scholar]
- Observation of room-temperature deep-red/near-IR phosphorescence of pyrene with cycloplatinated complexes: An experimental and theoretical study. European Journal of Inorganic Chemistry. 2010;28:4470-4482. https://doi.org/10.1002/ejic.201000488.
- [Google Scholar]
- Harnessing aggregation-induced emission property of indolizine derivative as a fluorogenic bioprobe for endoplasmic reticulum. Dyes Pigments. 2022;200:110118. https://doi.org/10.1016/j.dyepig.2022.110118.
- [Google Scholar]
- Molecular rotor based on dipyridylphenylamine: Near-infrared enhancement emission from restriction of molecular rotation and applications in viscometer and bioprobe. Dyes and Pigments. 2020;172:107795. https://doi.org/10.1016/j.dyepig.2019.107795.
- [Google Scholar]
- A bifunctional mitochondrial targeting AIE-active fluorescent probe with high sensitivity to hydrogen peroxide and viscosity for fatty liver diagnosis. New Journal of Chemistry. 2021;45:12138. https://doi.org/10.1039/D1NJ01712H.
- [Google Scholar]
- An acidic pH independent Piperazine-TPE AIEgen as a unique bioprobe for lysosome tracing. Chemical Science. 2017;8:7593-7603. https://doi.org/10.1039/c7sc03515b.
- [Google Scholar]
- Mechanistic analysis of viscosity-sensitive fluorescent probes for applications in diabetes detection. Journal of Materials Chemistry, B: Materials for Biology and Medicine. 2024;12:2917-2937. https://doi.org/10.1039/d3tb02697c.
- [Google Scholar]
- Developing iron and ruthenium complexes for potential nonlinear optical applications. Coordination Chemistry Reviews. 2013;257:1438-1458. http://dx.doi.org/10.1016/j.ccr.2012.06.025.
- [Google Scholar]
- Synergistic enhanced optical limiting property of graphene oxide hybrid materials functionalized with Pt complexes. ACS Applied Materials & Interfaces. 2017;9:33029-33040. https://doi.org/10.1021/acsami.7b10585.
- [Google Scholar]
- A theoretical study on the second-order nonlinear optical properties of Pt(II) bis-acetylide complexes: Substituent and redox effects. Physical Chemistry Chemical Physics: PCCP. 2024;26:6862-6871. https://doi.org/10.1039/d3cp04418a.
- [Google Scholar]
- Redox-triggered switch based on platinum(II) acetylacetonate complexes bearing the isomeric donor−acceptor conjugation ligand showing high second-order nonlinear optical response. New Journal of Chemistry. 2019;43:11263-11274. https://doi.org/10.1039/C9NJ02183C.
- [Google Scholar]
- High performance Pt(II) complex and its hybridized carbon quantum dots: Synthesis and the synergistic enhanced optical limiting property. Applied Surface Science. 2022;584:152567. https://doi.org/10.1016/j.apsusc.2022.152567.
- [Google Scholar]
- The effect of monodentate co-ligands on the properties of Pt(II) complexes bearing a tridentate CˆN*N-Luminophore. Molecules. 2023;28:7834. https://doi.org/10.3390/molecules28237834.
- [Google Scholar]
- Glucose-appended platinum(II)-BODIPY conjugates for targeted photodynamic therapy in red light. Inorganic Chemistry. 2018;57:1717-1726. https://doi.org/10.1021/acs.inorgchem.7b02249.
- [Google Scholar]
- Cyclometalated platinum(II) 6-Phenyl-4-(9,9-dihexylfluoren-2-yl)-2,2′-bipyridine complexes: Synthesis, photophysics, and nonlinear absorption. Inorganic Chemistry. 2010;49:4507-4517. https://doi.org/10.1021/ic902281a.
- [Google Scholar]
- Construction of emissive ruthenium(II) metallacycle over 1000 nm wavelength for in vivo biomedical applications. Nature Communications. 2022;13:2009. https://doi.org/10.1038/s41467-022-29572-2.
- [Google Scholar]
- Recent advances in synthesis and photophysical applications of pyridine-based heterocycles. Asian Journal of Organic Chemistry. 2025;14:e202500004. https://doi.org/10.1002/ajoc.202500004.
- [Google Scholar]
- Some Pt(II)-complexes with dpb, Fdpb and F2dpb ligands as potent anticancer agents and their mode of interaction with AT/GC base pairs: A DFT study. Journal of the Indian Chemical Society. 2023;100:100923. https://doi.org/10.1016/j.jics.2023.100923.
- [Google Scholar]
- New minor groove covering DNA binding mode of dinuclear Pt(II) complexes with various pyridine-linked bridging ligands and dual anticancer-antiangiogenic activities. Journal of Biological Inorganic Chemistry. 2020;25:395-409. https://doi.org/10.1007/s00775-020-01770-7.
- [Google Scholar]
- An AIEgen and Iodine double-ornamented platinum(II) complex for bimodal imaging-guided chemo-photodynamic combination therapy. Small. 2024;20:2309894. https://doi.org/10.1002/smll.202309894.
- [Google Scholar]
- Synthesis and anticancer mechanisms of four novel platinum(II) 4’-substituted-2,2’:6’,2’’-terpyridine complexes. Dalton Transactions. 2024;53:2143-2152. https://doi.org/10.1039/D3DT03197G.
- [Google Scholar]
- Development of a pre-assembled TBET fluorescent probe for ratiometric sensing of anticancer platinum(II) complexes. Chemistry – An Asian Journal. 2020;15:1449-1455. https://doi.org/10.1002/asia.202000157.
- [Google Scholar]
- Photophysical study on DNA & BSA binding and cytotoxic behaviour of piperidine-Pt(II) complexes: Their kinetics & mechanism and molecular docking. Journal of Photochemistry and Photobiology A: Chemistry. 2023;441:114740. https://doi.org/10.1002/smll.202309894.
- [Google Scholar]