A series of diimine ligands has been designed on the basis of 2-pyridyl-1H-phenanthro[9,10-d]imidazole (L1, L2). Coupling the basic motif of L1 with anthracene-containing fragments affords the bichromophore compounds L3–L5, of which L4 and L5 adopt a donor–acceptor architecture. The latter allows intramolecular charge transfer with intense absorption bands in the visible spectrum (lowest λabs 464 nm (ε = 1.2 × 104 M–1 cm–1) and 490 nm (ε = 5.2 × 104 M–1 cm–1) in CH2Cl2 for L4 and L5, respectively). L1–L5 show strong fluorescence in a fluid medium (Φem = 22–92%, λem 370–602 nm in CH2Cl2); discernible emission solvatochromism is observed for L4 and L5. In addition, the presence of pyridyl (L1–L5) and dimethylaminophenyl (L5) groups enables reversible alteration of their optical properties by means of protonation. Ligands L1–L5 were used to synthesize the corresponding [Re(CO)3X(diimine)] (X = Cl, 1–5; X = CN, 1-CN) complexes. 1 and 2 exhibit unusual dual emission of singlet and triplet parentage, which originate from independently populated 1ππ* and 3MLCT excited states. In contrast to the majority of the reported Re(I) carbonyl luminophores, complexes 3–5 display moderately intense ligand-based fluorescence from an anthracene-containing secondary chromophore and complete quenching of emission from the 3MLCT state presumably due to the triplet–triplet energy transfer (3MLCT → 3ILCT).

Luminescent cyclometalated complexes [M(C^N^N)CN] (M=Pt, Pd; HC^N^N=pyridinyl‐ (M=Pt 1, Pd 5), benzyltriazolyl‐ (M=Pt 2), indazolyl‐ (M=Pt 3, Pd 6), pyrazolyl‐phenylpyridine (M=Pt 4)) decorated with cyanide ligand, have been explored as nucleophilic building blocks for the construction of halogen‐bonded (XB) adducts using IC6F5 as an XB donor. The negative electrostatic potential of the CN group afforded CN⋅⋅⋅I noncovalent interactions for platinum complexes 1–3; the energies of XB contacts are comparable to those of metallophilic bonding according to QTAIM analysis. Embedding the chromophore units into XB adducts 1–3⋅⋅⋅IC6F5 has little effect on the charge distribution, but strongly affects Pt⋅⋅⋅Pt bonding and π‐stacking, which lead to excited states of MMLCT (metal–metal‐to‐ligand charge transfer) origin. The energies of these states and the photoemissive properties of the crystalline materials are primarily determined by the degree of aggregation of the luminophores via metal–metal interactions. The adduct formation depends on the nature of the metal and the structure of the metalated ligand, the variation of which can yield dynamic XB‐supported systems, exemplified by thermally regulated transition 3↔3⋅⋅⋅IC6F5.

Strongly blue fluorescent 1-phenyl-2-(pyridin-2-yl)-1H-phenanthro[9,10-d]imidazole (L1) is a facile block for the construction of multichromophore organic molecules, and simultaneously serves as a chelating diimine ligand.