Novel Ferrocene‐Appended β‐Ketoimines and Related BF₂ Derivatives with Significant Aggregation‐Induced Emission and Second‐Order Nonlinear Optical Properties

Abstract

As eries of new b-ketoimines containing af errocene moiety and their BF 2 complexes have been synthesized and structurally characterized. The solvatochromism of the b-ketoimines was studied, putting in evidencearedshift with increasing solvent polarity.T his positive solvatochromism can be attributed to am ore polarizede xcited state compared with the grounds tate, due to intramolecular charge transfer( ICT) transitions. The b-ketoimines exhibited weak emission, attributable to the excited-state intramolecular proton transfer( ESIPT) phenomenon. This ESIPT effect is suppressedu ponr estriction of the keto-enaminet automerism, inducedu pon addition of BF 3 •OEt 2 ,w hich afforded the related BF 2 complexes, characterized by an enhancement of the fluorescence through the ICT effect. Both the b-ketoimines and BF 2 complexes exhibited significant aggregation-inducede mission behavior in mixtureso fC H 3 CN/H 2 O, due to restriction of intramolecular rotationint he aggregated state. The frontier molecular orbital levels,g round-and excitedstate dipole moments (m g and m e ), and the origin of electronic absorption spectra were studied by time-dependent DFT calculations. The second-order nonlinearo ptical (NLO) properties were determined by the electric-field-induced secondharmonic generation technique. The mb 1907 values of the bketoimines increased upon the formationo ft he related BF 2 complexes,m ainly due to an enhancement of the groundstate dipole moment. The resultsp resented here reveal that some of these novel compounds are excellent multifunctional candidates for NLO and luminescence applications.

Ferrocene functionalized enantiomerically pure Schiff bases and their Zn(ii) and Pd(ii) complexes: a spectroscopic, crystallographic, electrochemical and computational investigation

“…[23][24][25] Schiff bases, characterized by an imine (4CQN-) or an azomethine (-CHQN-) group, 26,27 form an outstanding class of proligands that play a key role in the development of coordination chemistry due to their facile synthesis, structural flexibility, easily tunable electronic properties, selectivity and sensitivity towards the coordinated metal ion and their ability to form stable complexes under various coordination geometries and oxidation states. 22,[28][29][30] Transition-metal complexes of Schiff base ligands have been widely investigated because of their applications in various branches of science such as in catalysis, [31][32][33] sensing, [34][35][36] as NLO molecular materials, 23,[37][38][39] and in biochemistry, [40][41][42] among others. Ferrocene substituted asymmetric N 2 O 2 -tetradentate Schiff bases are generally obtained upon condensation of salicylaldehyde or its derivatives with a preformed tridentate organometallic precursor bearing a free amino group.…”

Synthesis and Electrochemical Behavior of Ferrocenyl β‐Ketoamines FcC(O)CH=C(NH(C6H4‐4‐R‘))R

“…During the course of the reaction of 1 or 2 with the appropriate amines 3 a – d the OH resonance signal (15.9 ppm ( 1 ); 16.4 ppm ( 2 )) disappears, while a new broad NH signal at ca. 12.5 ppm appears, as characteristic for the formation of enaminones 4 a – d and 5 a – d , respectively, [18c] allowing to control the progress of the reaction. The 13 C{ 1 H} NMR spectra of the title compounds are characterized by the typical Fc resonance signals (68–83 ppm), the p ‐substituted C 6 H 4 building block and especially the carbonyl resonance signal at ca.…”

“…However β ‐ketoamines of type FcC(O)CH=C(NHR)Fc (Fc=Fe( η 5 ‐C 5 H 4 )( η 5 ‐C 5 H 5 ) have not been reported so far. Furthermore, the study of electron‐transfer and electronic interactions within ferrocenyl substituted β ‐ketoamines has mainly been neglected [1,18] and generally refers to β ‐ketoamine metal complexes [10a–f,18b,c,19] …”

An excursion in the second-order nonlinear optical properties of platinum complexes

“…Luminescent coordination compounds with good quadratic hyperpolarizabilities are interesting multifunctional molecular materials [39,[67][68][69][70][71]. For this reason, the quadratic hyperpolarizabilities of luminescent Pt(II) compounds, with a β-diketonate and a cyclometalated 2phenylpyridine, were studied by the EFISH method in chloroform.…”

“…Thus, an EFISH investigation was accomplished, in CH2Cl2 solution, on two photochromic cyclometalated phenylbipyridine platinum(II) complexes with an acetylide DTE ancillary ligand bearing a phenyl (71) or dimethylaminophenyl (72) group (Figure 17) [108].…”