# Metal-Coordinated Polymer-Inorganic Hybrids: Synthesis, Properties, and Application
## 3 Polymer-Inorganic Coordinated Hybrids: Complexation-Induced Properties
### Pyridine-Based Polymers
#### 3.1.4 Photophysical Properties of Coordination of P4 VP with Metal Ions  
Few studies have explored the impact of incorporating transition metals into polymers, which results in altered photophysical properties of the complex system. In a notable study, [PERSON] et al. [99] explore the coordination behavior of poly(4-vinylpyridine) (P4 VP) with two metal cations, Au(I) and Zn(II), forming luminescent metal-containing polymers. The synthesis of these metal-containing polymers involves reacting P4 VP with gold and zinc precursors specifically, (Me2S)AuCI for the gold complex and ZnCl2 for the zinc complex (Figure 6a). Upon coordination, the polymers formed are insoluble in most common organic solvents, with the empirical formulas of (PVP)(AuCI)0.4 and (PVP)(ZnCl2)0.7. The Zn(II) complex was found to be highly crosslinked, while the Au(I) complex remained soluble in dimethyl sulfoxide (DMSO). The photophysical properties of these metal-containing polymers were analyzed, revealing that both P4 VP-Au(I) and P4 VP-Zn(II) complexes exhibit luminescence upon UV light excitation. The luminescence of the P4 VP-Au(I) complex is primarily attributed to aurophilic interactions, where gold-gold (AuAu) contacts contribute to the emission properties. On the other hand, the luminescence of the P4 VP-Zn(II) complex is excitation wavelength-dependent, which is proposed to result from the formation of aggregated species with different excitation energies. These aggregates create a complex emission profile that varies with the wavelength of excitation.  
Figure 6: (**a**) Preparation of P4 VP-Au (I) polymer complex: the synthesis involves the coordination of poly(4-vinylpyridine) (P4 VP) with (Me2S)AuCI in a mixture of ethanol (EtOH) and dichloromethane (DCM) at room temperature [99]. (**b**) Suggested structural model showing intrachain and interchain aurophilic interactions in metallopolymers 1 and 2 [114]. Adapted with permission from the American Chemical Society [114].  
In a similar study, [PERSON] et al. [114]. investigate the synthesis, photophysical properties, and structural aspects of a novel class of gold-based metallopolymers. These metallopolymers are formed by coordinating P4 VP with pentahalophenyl-gold(I) precursors, resulting in materials with intriguing phosphorescent properties and enhanced thermal and photonic stability. Two metallopolymers, [Au(C\({}_{6}\)F\({}_{5}\))PVP] (1) and [Au(C\({}_{6}\)Cl\({}_{5}\))PVP] (2), were synthesized by reacting P4 VP with the respective gold(I) precursors. One of the most striking properties of these metallopolymers is their bright photoluminescence (PL) in the solid state. Temperature-dependent PL spectra reveal that both 1 and 2 exhibit tunable emission maxima based on the excitation wavelength, with luminescence colors ranging from blue to yellow, depending on the temperature. This thermochromic luminescence is highly sensitive to temperature, which indicates the presence of active triplet (T1) states within the metallopolymers. The paper similarly suggests that the emission properties and stability of these metallopolymers are due to aurophilic (Au(I)\(\cdots\)Au(I)) interactions within the polymer matrix. These interactions are both intra- and interchain, forming a network that stabilizes the material's luminescent state. A structural model, illustrated in Figure 6b, shows these interactions, where each Au(I) ion is influenced by neighboring Au(I) centers. This structural feature enables the metallopolymers to maintain phosphorescent properties across a range of temperatures and excitation conditions. The paper discusses the potential for these metallopolymers to be used in polymer light-emitting diodes (PLEDs), leveraging their high solid-state quantum yields, energy-rich triplet excitons, and fast phosphorescence lifetimes.