Luminescence Solvato- and Vapochromism of Alkynyl-Phosphine Copper Clusters

The reaction of [Cu(NCMe)4][PF6] with aromatic acetylenes HC2R and triphosphine 1,1,1-tris(diphenylphosphino)methane in the presence of NEt3 results in the formation of hexanuclear Cu(I) clusters with the general formula [Cu6(C2R)4{(PPh2)3CH}2][PF6]2 (R = 4-X-C6H4 (1-5) and C5H4N (6); X = NMe2 (1), OMe (2), H (3), Ph (4), CF3 (5)). The structural motif of the complexes studied consists of a Cu6 metal core supported by two phosphine ligands and stabilized by σ- and π-coordination of the alkynyl fragments (together with coordination of pyridine nitrogen atoms in cluster 6). The solid state structures of complexes 2-6 were determined by single crystal XRD analysis. The structures of the complexes in solution were elucidated by (1)H, (31)P, (1)H-(1)H COSY NMR spectroscopy, and ESI mass spectrometry. Clusters 1-6 exhibit moderately strong phosphorescence in the solid state with quantum yields up to 17%. Complexes 1-5 were found to form solvates (acetone, acetonitrile) in the solid state. The coordination of loosely bound solvent molecules strongly affects emission characteristics and leads to solvato- and vapochromic behavior of the clusters. Thus, solvent-free and acetonitrile solvated forms of 3 demonstrate contrasting emission in orange (615 nm) and blue (475 nm) regions, respectively. The computational studies show that alkynyl-centered IL transitions mixed with those of MLCT between the Cu6 metal core and the ligand environment play a dominant role in the formation of excited states and can be considerably modulated by weakly coordinating solvent molecules leading to luminescence vapochromism.This research has been supported by St. Petersburg State University Research Grant 0.37.169.2014, and Russian Foundation for Basic Research Grants 13-03-00970, 14-03-32077, and 13-03-12411. Academy of Finland (Grant 268993/2013, I.O.K), University of Eastern Finland (strategic funding—Russian–Finnish collaborative project), is also gratefully acknowledged. The work was carried out using equipment of the Analytical Center of Nano- and Biotechnologies of SPbSPU with financial support of the Ministry of Education and Science of Russian Federation; Centers for Magnetic Resonance, X-ray Diffraction Studies, Chemical Analysis and Materials Research, Optical and Laser Materials Research; and Computer Center of St. Petersburg State University

Luminescence solvato-and vapochromism of alkynyl-phosphine copper clusters

The reaction of [Cu(NCMe)4][PF6] with aromatic acetylenes HC2R and triphosphine 1,1,1-tris(diphenylphosphino)methane in the presence of NEt3 results in the formation of hexanuclear Cu(I) clusters with the general formula [Cu6(C2R)4{(PPh2)3CH}2][PF6]2 (R = 4-X-C6H4 (1–5) and C5H4N (6); X = NMe2 (1), OMe (2), H (3), Ph (4), CF3 (5)). The structural motif of the complexes studied consists of a Cu6 metal core supported by two phosphine ligands and stabilized by σ- and π-coordination of the alkynyl fragments (together with coordination of pyridine nitrogen atoms in cluster 6). The solid state structures of complexes 2–6 were determined by single crystal XRD analysis. The structures of the complexes in solution were elucidated by 1H, 31P, 1H–1H COSY NMR spectroscopy, and ESI mass spectrometry. Clusters 1–6 exhibit moderately strong phosphorescence in the solid state with quantum yields up to 17%. Complexes 1–5 were found to form solvates (acetone, acetonitrile) in the solid state. The coordination of loosely bound solvent molecules strongly affects emission characteristics and leads to solvato- and vapochromic behavior of the clusters. Thus, solvent-free and acetonitrile solvated forms of 3 demonstrate contrasting emission in orange (615 nm) and blue (475 nm) regions, respectively. The computational studies show that alkynyl-centered IL transitions mixed with those of MLCT between the Cu6 metal core and the ligand environment play a dominant role in the formation of excited states and can be considerably modulated by weakly coordinating solvent molecules leading to luminescence vapochromism

Silver Alkynyl-Phosphine Clusters: An Electronic Effect of the Alkynes Defines Structural Diversity

The face-capping triphosphine, 1,1,1-tris­(diphenyl­phos­phino)­methane (tppm), together with bridging alkynyl ligands and the counterions, facilitates the formation of a family of silver complexes, which adopt cluster frameworks of variable nuclearity. The hexanuclear compounds [Ag₆­(C₂­C₆H₄-4-X)₃­(tppm)₂­(An^–)₃] (X = H (<b>1</b>), CF₃ (<b>2</b>), OMe (<b>3</b>), An^– = CF₃SO₃^–; X = OMe (<b>4</b>), An^– = CF₃COO^–) are produced for the electron-accepting to moderately electron-donating alkynes and the appropriate stoichiometry of the reagents. <b>1</b> and <b>3</b> undergo an expansion of the metal core when treated with 1 equiv of Ag⁺ to give the species [Ag₇­(C₂­C₆H₄-4-X)₃­(tppm)₂­(CF₃­SO₃)₃]­(CF₃­SO₃) (X = H (<b>5</b>), OMe (<b>6</b>)). The electron-donating substituent (X = NMe₂) particularly favors this Ag₇ arrangement (<b>7</b>) that undergoes geometry changes upon alkynylation, resulting in the capped prismatic cluster [Ag₇­(C₂­C₆H₄-4-NMe₂)₄­(tppm)₂­(CF₃­SO₃)]­(CF₃­SO₃)₂ (<b>8</b>). Alternatively, for the aliphatic <i>^t</i>Bu-alkyne, only the octanuclear complex [Ag₈­(C₂Bu^<i>t</i>)₄­{(PPh₂)₃­CH}₂­(CF₃­SO₃)₂]­(CF₃­SO₃)₂ (<b>9</b>) is observed. The structures of <b>1</b>–<b>4</b> and <b>6</b>–<b>9</b> were determined by X-ray diffraction analysis. In solution, all the studied compounds were found to be stereochemically nonrigid that prevented their investigation in the fluid medium. In the solid state, clusters <b>2</b>, <b>3</b>, <b>5</b>–<b>8</b> exhibit room temperature luminescence of triplet origin (maximum Φ_em = 27%, λ_em = 485–725 nm). The observed emission is assigned mainly to [<i>d</i>(Ag) → π*­(alkyne)] electronic transitions on the basis of TD-DFT computational analysis

Silver Alkynyl-Phosphine Clusters: An Electronic Effect of the Alkynes Defines Structural Diversity

The face-capping triphosphine, 1,1,1-tris­(diphenyl­phos­phino)­methane (tppm), together with bridging alkynyl ligands and the counterions, facilitates the formation of a family of silver complexes, which adopt cluster frameworks of variable nuclearity. The hexanuclear compounds [Ag₆­(C₂­C₆H₄-4-X)₃­(tppm)₂­(An^–)₃] (X = H (<b>1</b>), CF₃ (<b>2</b>), OMe (<b>3</b>), An^– = CF₃SO₃^–; X = OMe (<b>4</b>), An^– = CF₃COO^–) are produced for the electron-accepting to moderately electron-donating alkynes and the appropriate stoichiometry of the reagents. <b>1</b> and <b>3</b> undergo an expansion of the metal core when treated with 1 equiv of Ag⁺ to give the species [Ag₇­(C₂­C₆H₄-4-X)₃­(tppm)₂­(CF₃­SO₃)₃]­(CF₃­SO₃) (X = H (<b>5</b>), OMe (<b>6</b>)). The electron-donating substituent (X = NMe₂) particularly favors this Ag₇ arrangement (<b>7</b>) that undergoes geometry changes upon alkynylation, resulting in the capped prismatic cluster [Ag₇­(C₂­C₆H₄-4-NMe₂)₄­(tppm)₂­(CF₃­SO₃)]­(CF₃­SO₃)₂ (<b>8</b>). Alternatively, for the aliphatic <i>^t</i>Bu-alkyne, only the octanuclear complex [Ag₈­(C₂Bu^<i>t</i>)₄­{(PPh₂)₃­CH}₂­(CF₃­SO₃)₂]­(CF₃­SO₃)₂ (<b>9</b>) is observed. The structures of <b>1</b>–<b>4</b> and <b>6</b>–<b>9</b> were determined by X-ray diffraction analysis. In solution, all the studied compounds were found to be stereochemically nonrigid that prevented their investigation in the fluid medium. In the solid state, clusters <b>2</b>, <b>3</b>, <b>5</b>–<b>8</b> exhibit room temperature luminescence of triplet origin (maximum Φ_em = 27%, λ_em = 485–725 nm). The observed emission is assigned mainly to [<i>d</i>(Ag) → π*­(alkyne)] electronic transitions on the basis of TD-DFT computational analysis

Silver Alkynyl-Phosphine Clusters: An Electronic Effect of the Alkynes Defines Structural Diversity

The face-capping triphosphine, 1,1,1-tris­(diphenyl­phos­phino)­methane (tppm), together with bridging alkynyl ligands and the counterions, facilitates the formation of a family of silver complexes, which adopt cluster frameworks of variable nuclearity. The hexanuclear compounds [Ag₆­(C₂­C₆H₄-4-X)₃­(tppm)₂­(An^–)₃] (X = H (<b>1</b>), CF₃ (<b>2</b>), OMe (<b>3</b>), An^– = CF₃SO₃^–; X = OMe (<b>4</b>), An^– = CF₃COO^–) are produced for the electron-accepting to moderately electron-donating alkynes and the appropriate stoichiometry of the reagents. <b>1</b> and <b>3</b> undergo an expansion of the metal core when treated with 1 equiv of Ag⁺ to give the species [Ag₇­(C₂­C₆H₄-4-X)₃­(tppm)₂­(CF₃­SO₃)₃]­(CF₃­SO₃) (X = H (<b>5</b>), OMe (<b>6</b>)). The electron-donating substituent (X = NMe₂) particularly favors this Ag₇ arrangement (<b>7</b>) that undergoes geometry changes upon alkynylation, resulting in the capped prismatic cluster [Ag₇­(C₂­C₆H₄-4-NMe₂)₄­(tppm)₂­(CF₃­SO₃)]­(CF₃­SO₃)₂ (<b>8</b>). Alternatively, for the aliphatic <i>^t</i>Bu-alkyne, only the octanuclear complex [Ag₈­(C₂Bu^<i>t</i>)₄­{(PPh₂)₃­CH}₂­(CF₃­SO₃)₂]­(CF₃­SO₃)₂ (<b>9</b>) is observed. The structures of <b>1</b>–<b>4</b> and <b>6</b>–<b>9</b> were determined by X-ray diffraction analysis. In solution, all the studied compounds were found to be stereochemically nonrigid that prevented their investigation in the fluid medium. In the solid state, clusters <b>2</b>, <b>3</b>, <b>5</b>–<b>8</b> exhibit room temperature luminescence of triplet origin (maximum Φ_em = 27%, λ_em = 485–725 nm). The observed emission is assigned mainly to [<i>d</i>(Ag) → π*­(alkyne)] electronic transitions on the basis of TD-DFT computational analysis