Record Multiphoton Absorption Cross-Sections by Dendrimer Organometalation

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Organic π-delocalizable frameworks are explored for multiphoton absorption (MPA).
• Tuning MPA properties often involves complex molecular design and synthesis.

Purpose of the Study:

• To enhance molecular two-, three-, and four-photon absorption (MPA) in organic frameworks.
• To investigate the effect of incorporating organometallic ruthenium units on MPA properties.

Main Methods:

• Synthesis of ruthenium alkynyl-containing dendrimers.
• Characterization of molecular absorption properties, including MPA cross-sections.
• Evaluation of solubility, redox switchability, and optical transparency.

Main Results:

• Achieved large increases in two-photon absorption and measurable three-photon absorption.
• Recorded record molecular four-photon absorption, an order of magnitude greater than previous records.
• Demonstrated strong MPA activity in the near-infrared biological and telecommunications windows.
• Observed enhanced solubility and reversible redox switchability of optical properties.
• Showed that increasing ruthenium content boosted MPA without compromising optical transparency.

Conclusions:

• Incorporation of bis(diphosphine)ruthenium units into organic π-frameworks significantly enhances MPA performance.
• Ruthenium alkynyl dendrimers are promising for applications requiring strong MPA in the near-infrared spectrum.
• The observed improvements in MPA are scalable with molecular weight and π-electron count.