The photophysical and electrochemical properties of copper (I) complexes are governed by two key factors: the flexibility of the ligand and the steric environment surrounding the copper ion. Given the preference of the copper (I) ion for tetrahedral geometry and the copper (II) ion for square planar, the choice of ligand plays a crucial role in determining the resulting geometry of the complex in the ground and excited states. A comparative analysis between the 2,9-dimethylphenanthroline ligand with the 2-2'biquinoline ligand reveals that the latter being more flexible allows the pseudo-Jahn Teller distortion in the excited state, thereby mitigating the luminescence quenching. Moreover, enhancing the steric hindrance within the complex prevented the pseudo-Jahn Teller distortion, however, too much steric hindrance in the ligands led to diminished stability of the complexes. Hence, this led to the rise of the HETPHEN strategy for crafting heteroleptic copper (I) complexes by employing combination of two ligands -one with high and one with low steric demand (Figure ). This modification not only prevented ligand exchange in solution; but also, could introduce a directionality of electron transfer provided one ligand is more electron deficient than the other.