Cyanide‐Assembled d10 Coordination Polymers and Cycles: Excited State Metallophilic Modulation of Solid‐State Luminescence.

Abstract: The series of cyanide‐bridged coordination polymers [(<italic><bold>P</bold></italic>^{<bold>2</bold>})CuCN]_{<italic>n</italic>} (<bold>1</bold>), [(<italic><bold>P</bold></italic>^{<bold>2</bold>})Cu{M(CN)₂}]_{<italic>n</italic>} (M=Cu <bold>3</bold>, Ag <bold>4</bold>, Au <bold>5</bold>) and molecular tetrametallic clusters [{(<italic><bold>P</bold></italic>^{<bold>4</bold>})MM'(CN)}₂]²⁺ (MM′=Cu₂<bold>6</bold>, Ag₂<bold>7</bold>, AgCu <bold>8</bold>, AuCu <bold>9</bold>, AuAg <bold>10</bold>) were obtained using the bidentate <italic><bold>P</bold></italic>^{<bold>2</bold>} and tetradentate <italic><bold>P</bold></italic>^{<bold>4</bold>} phosphane ligands (<italic><bold>P</bold></italic>^{<bold>2</bold>}=1,2‐bis(diphenylphosphino)benzene; <italic><bold>P</bold></italic>^{<bold>4</bold>}=tris(2‐diphenylphosphinophenyl)phosphane). All title complexes were crystallographically characterized to reveal a zig‐zag chain arrangement for <bold>1</bold> and <bold>3</bold>–<bold>5</bold>, whereas <bold>6</bold>–<bold>10</bold> possess metallocyclic frameworks with different degree of metal‐metal bonding. The d¹⁰–d¹⁰ interactions were evaluated by the quantum theory of atoms in molecules (QTAIM) computational approach. The photophysical properties of <bold>1</bold>–<bold>10</bold> were investigated in the solid state and supported by theoretical analysis. The emission of compounds <bold>1</bold> and <bold>3</bold>–<bold>5</bold>, dominated by metal‐to‐ligand charge transfer (MLCT) transitions located within {Cu<italic><bold>P</bold></italic>^{<bold>2</bold>}} motifs, is compatible with thermally activated delayed fluorescence (TADF) behaviour and a small energy gap between the <italic>T₁</italic> and <italic>S₁</italic> excited states. The luminescence characteristics of <bold>6</bold>–<bold>10</bold> are strongly dependent on the composition of the metal core; the emission band maxima vary in the range 484–650 nm with quantum efficiency reaching 0.56 (<bold>6</bold>). The origin of the emission for <bold>6</bold>–<bold>8</bold> and <bold>10</bold> at room temperature is assigned to delayed fluorescence. AuCu cluster <bold>9</bold>, however, exhibits only phosphorescence that corresponds to theoretically predicted large value Δ<italic>E</italic>(<italic>S₁</italic>−<italic>T₁</italic>). DFT simulation highlights a crucial impact of metallophilic bonding on the nature and energy of the observed emission, the effect being greatly enhanced in the excited state. [ABSTRACT FROM AUTHOR]