Platinum terpyridyl complexes

Zhang D, Wu L-Z, Zhou L, et al. Photocatalytic hydrogen production from Hantzsch 1,4-dihydropyridines by platinum(II) terpyridyl complexes in homogeneous solution. / Am Chem Soc 2004 126 3440-1. 

Work on Ptn terpyridyl complexes has not been limited to just mononuclear systems. Yam and coworkers have also investigated complexes wherein two platinum centers are attached through alkynyl bridges more specifically they studied chromophores of the type f Hu. tpy )Ptf( =C)nI>tf Hu. tpy)]2+ (3.10) [65], These structures exhibit photoluminescence in both the solid state and in room temperature solutions, the latter assigned as 3CT in nature mixed with 3IL and 3LLCT character. 

Mono- or dinuclear platinum(II) complex capped with one or two [Pt(Bu3tpy)]+ units can be incorporated with Ln(hfac)3 units to produced a series of PtLn (Ln = Nd 88, Yb 89) and Pt2Ln (Ln = Nd 90, Yb 91) heteronuclear complexes [131]. With excitation at 350 nm < L < 550 nm, sensitized NIR lanthanide luminescence was detected in these Pt-Ln heteronuclear complexes with microsecond ranges of lifetimes, whereas Pt-based luminescence from the MLCT and LLCT states was mostly quenched. This reveals that fairly effective Pt Ln energy transfer is operating from the platinum(II) terpyridyl alkynyl chromophores to the lanthanide(III) centers. 

In the same regard, platinum(II) terpyridyl complexes (18) earn attention too. For the derivatives with X = Ph, the low-energy bands (460-600 nm) are assigned to formal LLCT states that receive substantial contribution from closely lying MLCT levels. When X = Me or Cl, luminescence of much red-shift (680-800 nm) is from MMLCT owing to metal-metal interactions occurring in head-to-tail dimers or polymers.In a recent study, large solvatochromism of the diynyl complexes (X = C C=C-C=CH), presumably due to metal-metal and -stacked interactions, has been observed. The cyclometallated phenyl bipyridine complexes (19) also show tunable excited-state properties, and the dinuclear species can reflect the metal - metal interactions in the [da ... 

Fig. 4.29 Schematic representation of the platinum(II) terpyridyl complexes with P(Glu)...

SCN, n = 1 X = NH3, n = 2) [152]. McMillin and coworkers recently reported the photophysical properties of a series of platinum] n) terpyridyl complexes with different counter ions [153]. These classes of platinum]n) complexes have also been found to exhibit rich polymorphic properties and have been studied by Gray and coworkers [154]. 

The strong cr-donating ability of the alkynyl unit that is capable of raising the energy of the LF excited states, together with the interest in metal alkynyl systems, has led to the synthesis of the first series of luminescent alkynyl complexes of platinum]ii) terpyridine, [Pt]trpy)C=C-R], which was reported by Yam and coworkers [156]. The complexes were prepared in reasonable yields by reacting the platinum]ii) terpyridyl complex, [Pt]trpy)]NCMe)]]OTf)2, with various aryl-alkynes in the presence of sodium hydroxide or triethylamine in methanol [Scheme 10.20). 

Scheme 10.21. Molecular wire-like platinum(ii) terpyridyl complexes of different lengths.

Xing L-B, Yu S, Wang X-J, Wang G-X, Chen B. Zhang L-P, Tung C-H, Wu L-Z (2012) Reversible multistimuli-responsive vesicles formed by an amphiphilic cationic platinum (II) terpyridyl complex with a ferrocene unit in water. Chem Commun 48 10886-10888... 

The steric crowding introduced in the latter by the four ethyl substituents inhibits nucleophilic attack at platinum, so that complexes of this type tend to undergo substitution by a dissociative mechanism [89]. The complex of the more rigid ligand, 2,2, 2"-terpyridyl, Pt(terpy)Cl+, is found to be about 103 to 104 times more reactive to substitution than the dien analogue this is ascribed to steric strain [90], which is reflected in the short Pt—N bond to the central nitrogen (Pt-N some 0.03 A shorter than the other two Pt-N bonds) and N—Pt—N bond angles of 80-82°). 

Li, X.-L., Dai, F.-R., Zhang, L.-Y, et al (2007) Sensitization of lanthanide luminescence in heterotrinu-clear PtLn2 (Ln = Eu, Nd, Yb) complexes with terpyridyl-functionalized alkynyl by energy transfer from a platinum(II) alkynyl chromophore. Organometallics, 26, 4483. 

Platinum(II) terpyridyl acetylide complex, h, CH3CN10-94% yield. ... 

Scheme 10.20. Synthesis of mononuclear platinum(ii) terpyridyl alkynyl complexes.

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