The heat‐resistant properties towards thermal emission quenching of trans‐bis[(β‐iminomethyl)aryloxy]platinum(II) complexes bearing 3‐iminomethyl‐2‐naphtholato‐ (1), 1‐iminomethyl‐2‐naphtholato‐ (2), 2‐iminomethyl‐1‐naphtholato‐ (3), and 2‐iminomethyl‐1‐phenolato (4) moieties, and a mechanistic rationale of these properties, are described in this report. Complex 1 a, with N,N′‐dipentyl groups, exhibits intense red emission in 2‐methyl‐2,3,4,5‐tetrahydrofuran (2‐MeTHF) at 298 K, whereas the analogues 2 a–4 a are less or non‐emissive under the same measurement conditions. All four complexes are highly emissive at 77 K. The heat‐resistant properties toward thermal emission quenching (Φ298 K/Φ77 K) increase in the order 1 a (0.52)>2 a (0.09)>3 a (0.02)>>4 a (0.00). We investigated the emission decay and thermal‐deactivation processes using density functional theory (DFT), time‐dependent (TD) DFT, and double‐hybrid density functional theory (DHDF) calculations of N,N′‐diethyl forms 1 b–4 b, and discuss the results with a focus on the energy levels, molecular structures, and electronic configurations in the triplet excited states. The energy differences between the triplet metal–ligand charge transfer (3MLCT) state and minimum‐energy crossing point between the lowest triplet state and singlet ground state (MECP) increase in the order 1 a>2 a, 3 a>4 a, consistent with the experimental results for the heat‐resistant properties of these complexes. The origin of the present structure dependence of the 3MLCT–MECP energy gap is ascribed to the ease or difficulty of the high‐lying dσ* orbital participating in the MECP upon thermal structural distortion. The structure dependence in energy gaps between the π* and dσ* orbitals, which is key for facilitating the thermal deactivation process, is rationally correlated with the extent of aromaticity on the coordination platforms (1 b>(2 b, 3 b)>4 b).
