Abstract (EN):
Third-order nonlinear and linear optical properties of nickel(II) and copper(II) complexes with salen ligands, functionalised with electron donor/acceptor groups (DA-salen), have been investigated in solution by the Z-scan technique using an Nd:YAG laser (lambda(inc) = 1064 nm) and UV/Vis spectroscopy. The [M(DA-salen)] complexes exhibit positive nonresonant nonlinear refractive indexes (net) in the range 27.0-8.50 center dot 10(-21) m(2)W(-1) and nonlinear absorption coefficients (a(2)(I)) within the range 1.80-26.0 center dot 10(-17) mW(-1). The latter values correspond to less than 10% of the overall magnitude of the third-order susceptibility, vertical bar chi(3)vertical bar, which is the result of the absence of electronic transitions near lambda(inc) = 1064 nm. For the group of N-II complexes, the highest net values are exhibited by the complexes with aromatic diimine bridges and large pi-electron delocalisation, which leads to intense electronic charge-transfer bands (epsilon > 16000 mol(-1) dm(3) cm(-1)) in the region lambda = 275-500 nm. The complexes that exhibit charge-transfer bands near lambda(inc)/2 = 532 nm, also show the highest a(2)(I) values, a consequence of multiphoton absorption processes. For the group of Cult complexes, the highest net value is also observed by the complex that exhibits the most intense charge-transfer bands in the region lambda = 275-475 nm. Between Ni-II and Cu-II complexes with the same DA-salen ligands, those of copper show always higher net values, indicating that NLO responses can also be fine-tuned by the metal centre. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Language:
English
Type (Professor's evaluation):
Scientific
Contact:
acfreire@fc.up.pt
No. of pages:
9