## 4 Conclusions  
In conclusions, poly(1-vinyl-1,2,4-triazole-_co-N_-vinylcarbazole) copolymers with a weight-average molecular weight of 175-201 kDa were synthesized by free-radical polymerization of functional 1-vinyl-1,2,4-triazole and \(N\)-vinylcarbazole. In the resulting copolymers, the content of N-vinylcarbazole units with hole conductivity varied from 9 to 37 mol %. On the basis of a polymeric ligand containing 1-vinyl-1,2,4-triazole, which has complexing properties, and a hole-conducting monomer \(N\)-vinylcarbazole, metal\(-\)polymer complexes with Tb\({}^{3+}\) ions in a polymethyl methacrylate matrix were obtained. Indeed, the terbium ion (III) was chosen because it does not require an additional sensitizer because of its intense luminescence in the complex with the polymeric ligand synthesized. In the case of europium or samarium ions (III), an additional low-molecular-weight sensitizer was required. The influence of the content of carbazole units in poly(1-vinyl-1,2,4-triazole-_co-N_-vinylcarbazole) on the luminescence intensity (\(I_{\rm 544}\)) of Tb\({}^{3+}\) ions and on excimer formation \(\chi_{\rm ex}\) was studied. The competition of two photophysical processes (formation of excimers between \(N\)-vinylcarbazole units and Forster energy transfer from VK to Tb\({}^{3+}\) ions) led to their differently directed effect on the degradation of the energy of absorbed photons, depending on the composition of the poly(VT-_co_-VK) copolymers, which manifested itself in the extreme behavior of the luminescence intensity of Tb\({}^{3+}\) ions. Owing to the combination of unique properties of VT and VK in the copolymer, the metal\(-\)polymer complexes obtained may be of interest in the structure of organo\(-\)inorganic composites as a luminescent probe. For example, in medicine, they can be used for imaging in obtaining the precursor of bone tissue, and replacing the terbium ion with its radioactive isotope allows for using this component as a therapeutic material in the treatment of osteosarcoma. In engineering, they can be used for the development of photosensitive layers of solar cells.  
**Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13084762/s1](https://www.mdpi.com/article/10.3390/app13084762/s1)]([https://www.mdpi.com/article/10.3390/app13084762/s1](https://www.mdpi.com/article/10.3390/app13084762/s1)), Figure S1: Deconvolution of photoluminescence spectra for MPC based on Tb\({}^{3+}\) ions and poly(VT-\(\infty\)-VK) copolymers with 9 (P1), 16 (P2), and 37 mol % (P3) of VK units in a photoinert PMMA matrix; Table S1: Parameters of photoluminescence and excitation electronic energy transferring (EET) rate in photoprocesses in PMMA films containing the MPC based on Tb\({}^{3+}\) and poly(VT-\(\infty\)-VK); Figure S2: Calibration curve for size-exclusion chromatography.  
**Author Contributions:** Conceptualization, R.S. and G.P.; methodology, S.K.; software, A.E.; investigation, A.E., T.N. and S.K.; data curation, T.N. and O.T.; writing--original draft preparation, R.S.; writing--review and editing, O.T.; supervision, G.P. and A.P.; project administration, R.S. and A.P. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Ministry of Science and Higher Education of the Russian Federation, grant number 121021700340-5.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The main results were obtained using the equipment of the Baikal Analytical Centre of collective using SB RAS.  
**Conflicts of Interest:** The authors declare no conflict of interest.