Two tetranuclear Au 2 Cu 2 cluster complexes [Au 2 Cu 2 (μ-(PPh 2 ) 2 py) 2 (μ-OH)](PF 6 ) 3 , 2, and [Au 2 Cu 2 Cl 2 (μ-(PPh 2 ) 2 py) 2 ](OTf) 2 , 4, have been prepared by the reactions of precursor complexes [Au 2 (μ-(PPh 2 ) 2 py) 2 ](OTf) 2 , 1, and [Cu 2 (μ-(PPh 2 ) 2 py) 2 (μ-SMe 2 )(OTf) 2 ], 3, with [Cu(NCCH 3 ) 4 ]PF 6 and AuCl(SMe 2 ), respectively. The crystal structures of complexes 2 and 4 were determined by X-ray crystallography, indicating a butterfly-shaped Au 2 Cu 2 metal core for 2 and a planar-shaped Au 2 Cu 2 metal core for 4. In complex 2, the Cu atoms occupy the edge-sharing bond, while in complex 4, alternating Au and Cu atoms occupy the tetragon vertices. The optical properties of the complexes were investigated by experimental and computational methods. Although complex 2 displayed a luminescence vapochromic behavior in the presence several volatile organic compounds, complex 4 indicated only an distinguishable change in its emission color when it was exposed to vapor of hydrogen-bond donor solvents. The calculations showed that 2 undergoes an unsymmetrical distortion in its two-coordinated gold(I) centers upon excitation to the first triplet excited state. This distortion induces a large Stokes shift and a strong rigidochromism behavior that is unprecedented for two-coordinated gold(I) complexes.

The six-coordinated silver­(I) complex [Au2Ag­(μ-(PPh2)2py)2­(OTf)2]­(OTf), 4 (py = pyridine, OTf = CF3SO3), and the five-coordinated silver­(I) complex [Au2Ag­(acetone)­(μ-(PPh2)2py)2]­(PF6)3, 6, were prepared by the reaction of the precursor complexes 1(OTf)2 and 1(PF6)2, in which 1 = [Au2(μ-(PPh2)2py)2]2+, with 1 equiv of Ag­(OTf) in dichloromethane and excess of Ag­(PF6) in a mixture of dichloromethane/acetone, respectively. Also, the five-coordinated silver­(I) complex [Au2Ag­(μ-(PPh2)2py)2(py)­(OTf)]­(OTf)2, 5, was obtained by the reaction of 4 with pyridine. The clusters 4–6 were characterized using multinuclear NMR spectroscopy and elemental microanalysis. The single-crystal X-ray diffraction analysis revealed the octahedral and distorted square pyramidal geometries around the silver­(I) centers in the crystal structures of 4 and 6, respectively; a dynamic structure was observed for cluster 5 due to pendulum motion of the Ag­(pyridine) moiety, which was anchored in the metallomacrocyclic unit [Au2(μ-(PPh2)2py)2]2+. Although the crystal structure of 6 did not display disorders for the silver atom and the acetone ligand similar to that observed for 5, the low-temperature NMR spectroscopies and calculations show a dynamic structure for cluster 6 due to linear motion of the Ag­(acetone) moiety. The reaction of the precursor complex 1(PO2F2)2 with 2 equiv of Ag­(PO2F2) yielded the tetranuclear Au2Ag2 cluster [Au2Ag2(PO2F2)2­(μ-(PPh2)2py)2]­(PO2F2)2, 7, with a planar-shaped {Au2Ag2} metal core in which alternating Au and Ag atoms occupy the tetragon vertices and showed a strong argentophillic interaction between the silver­(I) centers. All clusters 4–7 are emissive in the solid state, and the origins of their emissive excited states were determined using time-dependent density functional theory calculations. Cluster 7 showed a dual phosphorescence emission, which displays strong dependence of the contributions of each emissive component onto the excitation wavelength.

Symmetrical and unsymmetrical biscyclometalated platinum­(II) complexes [Pt­(ptpy)2], 1, and [Pt­(ptpy)­(bppy)], 2, in which ptpy = deprotonated 2-(p-tolyl)­pyridine and bppy = deprotonated 2-(3-bromophenyl)­pyridine, have been prepared from the reaction between tris­(pentafluorophenyl)­borane, B­(C6F5)3 and 1 equiv of monocyclometalated complexes [PtMe­(ptpy)­(ptpyH)], B, and [PtMe­(ptpy)­(bppyH)], C, respectively. The solid-state structures of 1 and 2 have been determined by X-ray crystallography. The reaction of 1 with 1 equiv of TlPF6 or [Au­(PPh3)]­OTF resulted in the production of heteronuclear complexes [Pt­(ptpy)2Tl]­PF6, 3 and {Pt­(ptpy)2[Au­(PPh3)]}­OTF, 4, respectively. X-ray diffraction data showed that in solid state, complex 4 exists as a mixture of supported and unsupported PtII–AuI-bonded structures, whereas complex 3 consists of an infinite helical chain structure built up by unsupported Pt–Tl dative bonds. Absorption, emission, and NMR spectroscopy data showed that both Pt–Tl and Pt–Au bonds in 3 and 4 have dynamic behavior. The low-temperature 1H, 31P­{1H}, and exchange spectroscopy NMR of 4 revealed two dynamic behaviors involving the rupture of the Au–C ipso bond as well as the dissociation–association of the [Au­(PPh3)]+ and Pt­(ptpy)2 fragments. All complexes displayed bright emission in the solid state, and their absorption and emission properties have been investigated both experimentally and by time-dependent density functional theory calculations.

Naphthalimide derivatives provide highly versatile self-assembled systems and aggregated forms with fascinating emission properties that make them potential candidates for many applications such as bioimaging and sensing. Although various aggregated species of naphthalimide derivatives have been well documented, little is known about the correlation between their structure and photophysical properties. Here the preparation of a series of tetrameric naphthalimide molecules in which naphthalimide units are linked by bis-N-heterocyclic carbene complexes of coinage metals is described. An in-depth structural investigation into these tetramers has been carried out in solution and the solid state using spectroscopic methods, X-ray crystallography, and computational methods. The experimental and calculated data indicate that the magnitude of the intramolecular interchromophoric π-interactions increases either by an increase in the metal ionic radius or on going from the solid to the solution state. These tetrameric naphthalimide compounds show intramolecular excimeric emissions in the solid and solution phases. However, the quantum yield efficiencies of these excimeric emissions show a trend similar to that for the intramolecular π-interactions either by going from the solution to the solid state or with an increase in the metal ionic radius. Surprisingly, the amine derivative analogues of the silver­(I) compound showed an unusual increase in the emission quantum yield efficiency to 92% in solution due to intramolecular hydrogen bonds between amine substituents on adjacent naphthalimde units.

Here, we report the synthesis and characterization of a binuclear Co(II) complex (Co2(2py)2Cl4) with two dinaphtho-diazacrown ether macrocyclic ligands, bearing two pyridine arms as a colourimetric and fluorescent sensor for...