Contrasted photochromic and luminescent properties in dinuclear Pt(ii) complexes linked through a central dithienylethene unit

Abstract

We disclose two unprecedented complexes built with a central dithienylethene photochrome connecting two cyclometalated Pt(ii) moieties either on the reactive carbon atoms or on the lateral non-reactive carbon atoms of the photochrome. The two systems show vastly different properties that are rationalised thanks to quantum-chemical calculations.

The switchable phosphorescence and delayed fluorescence of a new rhodamine-like dye through allenylidene formation in a cyclometallated platinum(ii) system

“…Similar to related cyclometallated alkynyplatinum(II) systems, 22,23,53 low-energy absorption bands at 412 nm and 430 nm (1) and 420 nm and 442 nm (2) were observed in their electronic absorption spectra in acetonitrile at room temperature (Figure S5a), assignable to the admixture of [dπ(Pt)→π*(N^N^C)] metal-toligand charge transfer (MLCT) and [pπ(C≡C)→π*(N^N^C)] ligand-to-ligand charge transfer (LLCT) transitions. Intense photoluminescence also found in the acetonitrile solution of 1 (λ max = 572 nm; τ = 215 and 660 ns) and 2 (λ max = 598 nm; τ = 151 ns) (Figure S5b), which are originated from the triplet excited state of 3 MLCT/ 3 LLCT character.…”

“…15,16 Incorporation of switchable organic units into optical-active transition metal complexes is one common strategy to achieve metal-based photo-functional materials with "ON" and "OFF" states in a controllable manner. [17][18][19][20][21][22][23][24][25][26][27][28] The design of multichromophoric systems capable of triplet sensitization and emission with a switching unit could lead to remote manipulation of the localization and the lifetime of the triplet emissive state.…”

“…We have been devoted to the exploration of possible combinations of transition metal complexes with photoswitchable and chemo-switchable units, such as photochromic diarylethenes (DTE) [22][23][24] and rhodamine-based derivatives, [43][44][45][46][47][48] respectively. As an extension of our ongoing interests in the controllable luminescence from the transition metal systems, our previous results prompted us to design and investigate novel rhodamine-based cyclometallated platinum(II) complexes.…”

An Enantiopure Cyclometallated Iridium Complex Displaying Long‐Lived Phosphorescence both in Solution and in the Solid State

“…Whilst it might be appealing to attribute both these unusual observations to the relative isolation of the helicene in the structure, it is interesting to note that the emission maxima are red-shifted compared to the values in solution, perhaps suggesting the involvement of dimeric or aggregate excited states that extend over two or more molecules in the solid state. [40] A closer look at the crystal structure revealed the presence of CH-π interactions between HÀ C(L4)-and the terminal ring of the [4]helicene unit (see Figure 2, HÀ C(L4)centroid interaction distance 3.020 Å) but no clear ππ interaction, although the compound does appear closely packed. Notwithstanding the lack of a fully convincing explanation, the empirical observation of intense, long-lived, and vibrationally structured photoluminescence in the solid state renders complex C particularly intriguing amongst the many cyclometallated Ir(III) phosphors reported to date.…”

Chromic Platinum Complexes Containing Multidentate Ligands

“…first reported the use of dithienylethene‐containing ligands to introduce photochromism in Pt(II) complexes in 2014 [109] . Since then, they have expanded this approach to produce analogous photochromic species, including mono‐ and binuclear Pt(II) complexes [110,111] . Similarly, Yam's group has utilized photoresponsive spirooxazines [112] and diarylethene units [113,114] to form photochromic bipyridine and alkynyl Pt(II) complexes.…”