Strategies to increase the quantum yield: Luminescent methoxylated imidazo[1,5-a]pyridines

Luminescent Imidazo[1,5‐a]pyridine Scaffold: Synthetic Heterocyclization Strategies‐Overview and Promising Applications

“…In particular, the typical quantum yield for impy derivatives is around 25%, [14,78,115,116] however, many products with a quantum yield at about 40% have been reported, [117,19,22] at the moment the highest reported value is 50% (see Scheme 17). [12] A remarkable large Stokes shift from 70 to 150 nm is characteristic of these emissive heterocycles that show good absorption in the UV range and intense emission in the visible spectrum. [32,33,64,92,117] Previous studies unravelled and rationalized the correlations between the chemical structure and the electronic properties, highlighting the key role of the rotation of the substituent group in position 1,3-substituted impy nucleus in increasing the emission quantum yield and influencing the frontier molecular orbitals.…”

“…[32,33,64,92,117] Previous studies unravelled and rationalized the correlations between the chemical structure and the electronic properties, highlighting the key role of the rotation of the substituent group in position 1,3-substituted impy nucleus in increasing the emission quantum yield and influencing the frontier molecular orbitals. [12,14,118] Even more noteworthy is the structural role of the chemical groups introduced in ortho on the substituent in positions 1 and 3 of the impy nucleus (see Scheme 17 substituted methoxy-impy). It is observed that the block of the rotation (of the aromatic ring in position 1 or 3) significantly increases the emission quantum yield.…”

“…In general, impy skeleton could be designed to obtain luminescent ligands from transition metal complexes, to connect other fluorophores (as BODIPY or rhodamine), [8][9][10][11] or to act as a fluorogenic centre itself. [12][13][14][15] To obtain these structural modifications it is of paramount importance to know the available different synthetic approaches to introduce functional groups, spacers or additional conjugated systems (such as imidazo-quinoline). [16][17][18][19][20][21] The distinctive emission of the impy moiety typically lies in the 450-530 nm range, with a large Stokes shift (up to 150 nm) and good quantum yield (ranging from 10% to 50%).…”

Dipyridylmethane Ethers as Ligands for Luminescent Ir Complexes

“…In particular, we reported different modification introducing amino, imino, nitrile, hydrazine and alcoholic functional groups, to increase the coordination stability and tune the optical properties. Moreover, the direct cyclization of di-2-pyridylketone (to form imidazo[1,5- a ]pyridine ligands) [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ] is widely reported to prepare emissive metal complexes [ 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. Furthermore, surface functionalization with luminescent ligands and corresponding complexes is attracting a high interest, with impact in catalysis, molecular electronics, analytical detection or sensor technology [ 26 , 27 ].…”

Microwave-Assisted Synthesis, Optical and Theoretical Characterization of Novel 2-(imidazo[1,5-a]pyridine-1-yl)pyridinium Salts

“…Imidazo [1,5-a]pyridines are a promising family of fluorophores that can be easily functionalized to tune their photophysical properties, characterized by a high photoluminescent quantum yield (up to 50%) and a large Stokes shift (up to 150 nm) [1][2][3][4]. The synthetic feasibility via a one-pot cyclocondensation reaction, without the use of any metal catalyst or highly sensitive Lewis acid, has been previously demonstrated [5,6].…”