## 3 Results and Discussion  
Xanthene, a moiety used in colorants, is capable of easily extending \(\pi\)-conjugation, which makes it generally appropriate for red or red-to-near-infrared dyes but unsuitable as a backbone for blue dyes [23]. On the other hand, triarylmethane is well-suited for blue dyes but suffers from poor photostability, requiring the introduction of various derivatives to improve its performance [24]. Conversely, pyrrole-based colorants exhibit remarkable optical, thermal, and electrochemical stability, offering vivid colors and enhanced functionality through adjustable wavelength absorption. Consequently, they are being investigated as sustainable, robust materials for applications in optoelectronic devices and high-performance coatings [25, 26]. A new blue colorant with excellent optical and thermal properties was designed for applications in color filters for image sensors. Pyrrole was selected as the core structure, and a cyano group was introduced to achieve an appropriate conjugation length. The pyrrole group exhibits strong light absorption characteristics, making it suitable for colorant materials in image sensors [18, 27]. To prevent molecular packing and improve solubility, alkyl groups in the form of butyl and hexyl were introduced. The absence of commercially available pyrrole-based blue materials poses challenges for direct comparison. Nevertheless, Disperse Blue 359, widely recognized as a blue dye, was chosen as a reference material because it allows for identifying commonalities in similar structures within the chemical formulas. Disperse Blue 359 is widely utilized in image sensor and color filter applications because of its remarkable optical performance, solvent compatibility, and thermal stability. On the basis of these strengths, this research focused on developing a new colorant with optimized absorption wavelengths and enhanced thermal stability characteristics. The final compounds, designated as BAPCP and HAPCP, were synthesized through dimerization, heterocyclization, and coupling reactions. The structures and synthetic routes of these compounds are detailed in Schemes 1 and 2. The two synthesized compounds showed no significant difference to the naked eye and exhibited a blue color (Figure S1). The structures of the synthesized compounds were confirmed using \({}^{1}\)H and \({}^{13}\)C NMR spectroscopy (Figures S2-S5). FT-IR analysis was performed to examine the characteristic functional groups of the synthesized compounds, with the measurement results illustrated in Figure S6. The synthesized novel compounds displayed similar FT-IR spectra, suggesting the presence of identical functional group characteristics. Analysis of the IR spectra indicated that the broad absorption band in the 3300-3500 cm\({}^{-1}\) region corresponds to N-H stretching vibrations. In the 2740-3000 cm\({}^{-1}\) region, sp\({}^{2}\) C-H stretching from the benzene ring and sp\({}^{3}\) C-H stretching from alkyl chains were detected. The strong absorption observed in the 2200-2260 cm\({}^{-1}\) region was attributed to C\(\equiv\)N triple bond stretching vibrations, and a pronounced absorption peak near 1710 cm\({}^{-1}\) was attributed to C=O stretching vibrations. In addition, sharp absorption peaks in the 1400-1600 cm\({}^{-1}\) range were associated with C=C stretching vibrations of the aromatic benzene ring, while CH\({}_{2}\) bending vibrations of alkyl chains appeared in the 800-1000 cm\({}^{-1}\) range. These findings confirm that the synthesized novel compounds contain specific functional groups consistent with the predicted molecular structure. The optical properties of the synthesized blue colorants, BAPCP and HAPCP, in solution are shown in Figure 1 and Table 1. The absorbance and transmittance of the synthesized pyrrole derivatives were measured in a 1.0 \(\times\) 10\({}^{-4}\) M solution in PGMEA, which is suitable for image sensor applications.