The energy gap law established for aromatic hydrocarbons and rare earth ions relates the nonradiative decay rate to the energy gap of a transition through a multiphonon emission process. We show that this energy gap law can be applied to the phosphoresce of a series of conjugated polymers and monomers for which the radiative decay rate has been enhanced through incorporation of a heavy metal. We find that the nonradiative decay rate from the triplet state T(1) increases exponentially with decreasing T(1)-S(0) gap for the polymers and monomers at 300 and 20 K. Comparison of the nonradiative decay of polymers with that of their corresponding monomers highlights the role of electron-lattice coupling.

The photophysical behavior of 3-chloro-7-methoxy-4-methylcoumarin related to the energy separation of the two lowest-lying singlet excited states Soluble, rigid-rod organometallic polymers trans-͓-Pt(PBu 3 n ) 2 -CwC-R-CwC-͔ ϱ ͑Rvbithienyl 2, terthienyl 3͒ have been synthesized in good yields by the CuI-catalyzed dehydrohalogenation reaction of trans-͓Pt(PBu 3 n ) 2 Cl 2 ͔ with one equivalent of the diterminal alkynyl oligothiophenes H-CwC-R-CwC-H in CH 2 Cl 2 / i Pr 2 NH at room temperature. We report the thermal properties, and the optical absorption, photoluminescence, and photocurrent action spectra of 1 ͑trans-͓ -Pt(PBu 3 n ) 2 -CwC-R-CwC-͔ ϱ , Rvthienyl͒, 2 and 3 as a function of the number of thiophene rings within the bridging ligand. With increasing thiophene content, the optical gap is reduced and the vibronic structure of the singlet emission changes toward that typical for oligothiophenes. We also find the intersystem crossing from the singlet excited state to the triplet excited state to become reduced, while the singlet-triplet energy gap remains unaltered. The latter implies that, in these systems, the T 1 triplet excited state is extended over several thiophene rings. The photoconducting properties do not depend on the size of the thiophene fragment. We discuss and compare our results with studies on oligothiophenes and related organometallic polymers.

We have studied the dependence of intersystem crossing and the spatial extent of singlet and triplet excitons in platinum-containing poly-yne polymers with the general formula [Pt(PR3)2C⋮CLC⋮C] n (R = Et, nBu; L = pyridine, phenylene, or thiophene) as a function of electron delocalization in the spacer group L. We also report the synthesis route of those compounds. The optical absorption, photoluminescence, and photoinduced absorption of the corresponding polymers and monomers have been measured. We find that conjugation is increased but intersystem crossing is reduced by the electron-rich thiophene unit, while the opposite occurs for the electron-deficient pyridine unit as compared to the phenylene unit. For all investigated systems, we find that the singlet excited state and a higher lying T n triplet excited state extend over more than a repeat unit while the T1 triplet state remains localized to less then one repeat unit.

The smallest band gap observed so far (1.77 eV) for an organometallic polymer is exhibited by the blue, rigid-rod polymer 2, which is prepared by the reaction of trans-[PtCl (PnBu ) ] with one equivalent of 1.

A series of protected and terminal dialkynes with extended pi-conjugation through a condensed aromatic linker unit in the backbone, 1,4-bis(trimethylsilylethynyl)naphthalene, 1,4-bis(ethynyl)naphthalene, 9,10-bis(trimethylsilylethynyl)anthracene, 9,10-bis(ethynyl)anthracene, have been synthesized and characterized spectroscopically. The solid-state structures of and have been confirmed by single crystal X-ray diffraction studies. Reaction of two equivalents of the complex trans-[Ph(Et(3)P)(2)PtCl] with an equivalent of the terminal dialkynes 1,4-bis(ethynyl)benzene and, in (i)Pr(2)NH-CH(2)Cl(2), in the presence of CuI, at room temperature, afforded the platinum(II) di-ynes trans-[Ph(Et(3)P)(2)Pt-C[triple bond, length as m-dash]C-R-C[triple bond, length as m-dash]C-Pt(PEt(3))(2)Ph](R = benzene-1,4-diyl; naphthalene-1,4-diyl and anthracene-9,10-diyl ) while reactions between equimolar quantities of trans-[((n)Bu(3)P)(2)PtCl(2)] and under similar conditions readily afforded the platinum(II) poly-ynes trans-[-((n)Bu(3)P)(2)Pt-C[triple bond]C-R-C[triple bond]C-](n)(R = naphthalene-1,4-diyl and anthracene-9,10-diyl ). The Pt(II) diynes and poly-ynes have been characterized by analytical and spectroscopic methods, and the single crystal X-ray structures of and have been determined. These structures confirm the trans-square planar geometry at the platinum centres and the linear nature of the molecules. The di-ynes and poly-ynes are soluble in organic solvents and readily cast into thin films. Optical spectroscopic measurements reveal that the electron-rich naphthalene and anthracene spacers create strong donor-acceptor interactions between the Pt(II) centres and conjugated ligands along the rigid backbone of the organometallic polymers. Thermogravimetry shows that the di-ynes possess a somewhat higher thermal stability than the corresponding poly-ynes. Both the Pt(II) di-ynes and the poly-ynes exhibit increasing thermal stability along the series of spacers from phenylene through naphthalene to anthracene.