Synthesis of a novel camphorquinone derivative having acylphosphine oxide group, characterization by UV-VIS spectroscopy and evaluation of photopolymerization performance

Abstract

Camphorquinone (CQ) derivatives having acylphosphine oxide (APO) group are unknown. This study synthesized such a novel 7,7-dimethyl-2,3-dioxobicyclo[2.2.1]heptane-1-carbonyldiphenyl phosphine oxide (DOHC-DPPO = CQ-APO). Ultraviolet and visible (UV-VIS) spectra of CQ-APO, CQ, and APO were measured. Photopolymerization performances of experimental light-cured resins comprising these photoinitiators were investigated. Newly synthesized CQ-APO showed as a pale yellow crystal (mp 365K). UV-VIS spectrum of CQ-APO showed two maximum absorption wavelengths (λmax) [372 nm (from APO group) and 475 nm (from CQ moiety)] within 350-500 nm. Unfilled resin containing CQ-APO exhibited good photopolymerization time (9.6 sec) and relaxed operation time (50 sec), as well as a pronouncedly lower b value (4.0) in the CIELab color specification system than that containing CQ (84.0). Resin composites containing CQ-APO, exhibited high flexural strength . It was concluded that CQ-APO possessed two λmax peaks within 350-500 nm, and that CQ-APO-containing resins exhibited excellent color tone, good photopolymerization reactivity, relaxed operation time, and high mechanical strength.

A review of the development of radical photopolymerization initiators used for designing light-curing dental adhesives and resin composites

“…As the latter value was approximately the same as that of CQ-APO, it could be said that the C-P Fig. 8 Schematic illustration of the synthesis of 7,7-dimethyl-2,3-dioxobicyclo[2.2.1]heptane-1-carbonyldiphenylphosphine oxide (CQ-APO) 8) . Full names of KA, CQ-COOH, CQ-COCl, and MDPP are given in Table 1.…”

“…As for CQ-COCl, it was synthesized by the reaction between 7,7-dimethyl-2,3-dioxobicyclo[2.2.1]-heptane-1-carboxylic acid (DOHCA=CQ-COOH) and thionyl chloride. Figure 9 shows the structural formulas of the photoinitiators or sensitizers and accelerators employed in the synthesis 8) , except CQ-APO. Figures 10−12 show the UV-VIS spectral behaviors of CQ-APO, CQ, and TMDPO in dry toluene before and after light irradiation with a dental halogen lamp.…”

“…Our recent study 8) thus newly designed and synthesized a novel 7,7-dimethyl-2,3-dioxobicyclo[2.2.1]heptane-1-carbonyl-diphenylphosphine oxide (DOHC-DPPO = CQ-APO). Figure 8 is a schematic illustration of the synthesis of CQ-APO, which was synthesized by Fig.…”

“…However, this new invention 33) did not resolve the key CQ-related problems, namely short operation time and a high b value which was manifested as a tinge of yellow. In light of these unresolved problems, a research study 8) was undertaken to develop a new photoinitiator which possessed reduced b value and high photopolymerization reactivity, but lengthened operation time -hence permitting a relaxed mode of therapeutic operation under ambient light.…”

“…In our recent study 8) , a novel CQ derivative bearing an APO group, i.e., 7,7-dimethyl-2,3-dioxobicyclo [2.2.1]heptane-1-carbonyl-diphenylphosphine oxide (DOHC-DPPO=CQ-APO) was synthesized. Its spectral behavior and photopolymerization reactivity were assessed to investigate its potential applicability in the design of light-curing resin composites.…”