Synthesis and photophysics of 4′-R-2,2′;6′,2″-terpyridyl (R = Cl, CN, N(CH3)2) platinum(II) phenylacetylide complexes

Abstract

Platinum terpyridyl (tpy) phenylacetylide complexes with -Cl, -CN, and -NMe(2) substituents on the 4'-position of the tpy ligand were synthesized and characterized. Their photophysical properties were systematically investigated. In addition, theoretical electronic structure calculations using density functional theory (DFT) and time-dependent (TD-DFT) approaches were carried out for complexes and ; the results of these calculations provided additional information on the nature of the electronic structures of the low-lying electronic states of these complexes, including the electron density distribution and the composition of the frontier molecular orbitals. Complexes exhibit moderately intense charge-transfer bands in the visible region, which are assigned to the (1)MLCT/(1)LLCT transitions. In comparison to their corresponding chloride complexes , these charge-transfer bands become broadened and red-shifted. Complexes emit at room temperature in CH(3)CN and CH(2)Cl(2) solutions and at 77 K in butyronitrile glassy solutions. At room temperature, the emission is tentatively attributed to (3)MLCT for and , and to a mixture of (3)MLCT/(3)ILCT/(3)pi,pi* for . Due to the admixture of (3)ILCT/(3)pi,pi* characters in its emitting state, displays a much higher emission quantum yield and longer emission lifetime compared to and . Replacing the chloride co-ligand in by phenylacetylide co-ligand clearly enhances the emission and prolongs the lifetime. exhibit a broad and moderately intense triplet excited-state absorption in the visible to the NIR region, with large excited-state absorption coefficients and moderately high triplet excited state quantum yields. Therefore, complexes , especially , have potential applications in organic light emitting devices (OLED) and as reverse saturable absorbing materials.

Platinum(II) Complexes Bearing 2‐(9,9‐Dihexadecyl‐7‐R‐fluoren‐2‐yl)‐1,10‐phenanthroline Ligands: Synthesis, Photophysics and Reverse Saturable Absorption

“…The τ 0 and k q for Pt‐ 1 – 6 are listed in Table 1. The k q values for these complexes are of the order 10 8 –10 9 L mol –1 s –1 , which are in accordance with the values reported for other C ∧ N ∧ N Pt complexes9e,12 and for Pt terpyridyl complexes 17…”

Structure–Property Relationships and 1O2 Photosensitisation in Sterically Encumbered Diimine PtII Acetylide Complexes

“…The extremely small thermally induced Stokes shift ( 5 : Δ E s =69 cm −1 ) confirms that emission from 5 and 7 is not derived from a charge‐transfer excited state and instead falls within the range expected for a 3 ππ* emissive state 16. 37b…”

“…[30b] The most significant feature in the spectra of complexes 3, 4 and 6 is a low-energy absorption band that is red-shifted with increasing electron-donating character of the acetylide. [14,15,37] This low-energy band, which is absent in L and Pt II precursor 1 and buried for the most part under the PAH absorption bands in 5 and 7, appears at highest energy in 4 (l = 401 nm), at 411 nm in 3 and at 445 nm for complex 6. The band is particularly sensitive to the polarity of the solvent and exhibits a significant degree of negative solvatochromism suggesting considerable involvement of charge transfer (e.g., in 6 the band occurs at 472 nm in toluene and 421 nm in acetonitrile).…”

Effect of pH/metal ion on the structure of metal–organic frameworks based on novel bifunctionalized ligand 4′-carboxy-4,2′:6′,4′′-terpyridine

“…8 49-Substituted-2,29:69,299-terpyridine is the most common in all ligands of forming metal complexes because of their electronic and steric versatility and the large p-conjugated structure. [9][10][11] In contrast to chelating 49-substituted-2,29:69,299-terpyridine, the bridging trigonal bifunctionalized ligand 49-carboxy-4,29:69,499-terpyridine (Hctpy, Chart 1), as a rigid ligand, may lead to the formation of nanosized cages, honeycomb porous frameworks and a Kagome ´structure [12][13][14] owing to two outer pyridyl rings and one carboxylic group tending to bond with metal ions.…”