Effect of carbazole and pyrrolidine functionalization of phenanthroline ligand on ground- and excited-state properties of rhenium(I) complexes. Interplay between 3MLCT and 3IL/3ILCT

• Published in: Dyes and pigments 2022-04, Vol.200, p.110113, Article 110113
• Main Authors: Palion-Gazda, Joanna, Machura, Barbara, Szłapa-Kula, Agata, Maroń, Anna M., Nycz, Jacek E., Ledwon, Przemyslaw, Schab-Balcerzak, Ewa, Siwy, Mariola, Grzelak, Justyna, Maćkowski, Sebastian
• Format: Article
• Language: English
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2022.110113

New rhenium(I) tricarbonyl complexes based on the phenanthroline ligand were designed and synthesized to investigate the role of carbazole (cbz) and pyrrolidine (pyrr) substituents in determining thermal, electrochemical and optoelectronic properties. Both pyrr and cbz are electron-releasing substituents, but they differ in the steric hindrance and electron delocalization ability. The impact of pyrr and cbz on ground- and excited-state properties of [ReCl(CO)3(cbz2-CH3phen)] (1) and [ReCl(CO)3(pyrr2-CH3phen)] (2) were investigated with a range of techniques including cyclic voltammetry, absorbance and emission spectroscopies, transient absorption spectroscopy, and they were discussed in comparison with the model chromophore [ReCl(CO)3(CH3phen)] (3). Experimental results were supported by theoretical calculations. The most striking difference between the pyrr and cbz groups was seen in their impact on the LUMO energy level. While the attached carbazole groups decreased the LUMO energy of 1, the pyrrolidine ones in 2 resulted in the rise of LUMO energy level compared to the model chromophore. For both 1 and 2, the HOMO got energetically destabilized in agreement with electro-donor abilities of pyrr and cbz substituents. Structural modification of phen backbone resulted also in changes of distribution of occupied MOs of 1 and 2 in relation to 3. Experimentally, it was manifested in noticeable changes of electrochemical and photophysical behaviour of the resulting Re(I) complexes in relation to the model chromophore. [Display omitted] •A series of Re(I) complexes with phen-like ligands was prepared.•The character of the ground and excited state of compounds was determined.•The effect of donor groups was explored experimentally and theoretically.