Structural Variation in Transition-Metal Bispidine Compounds

Abstract

A merocyanine dye with an outstandingly large dipole moment of 14 Debye affords thin‐film transistors with 0.18 cm2V−1s−1 hole mobility and a 106 on/off ratio. These results suggest that molecules that lack symmetry and possess large dipole moments can perform excellent charge carrier transport contrary to established molecular semiconductor design strategies.

Bispidine Coordination Chemistry

“…In many cases (but not exclusively), there is a long distance to N7 and a shorter one to N3. This situation has been studied and discussed in detail for the tetradentate ligand 14 and its derivatives (189), for the hexadentate ligands (69) and for the Jahn-Teller active copper(II) systems (71,82,194,199) (see Section III.D). Interestingly, this asymmetry usually has a strong influence on the distances and bond strengths of the in-plane and axial coligands X E and X A , where X A often (but not exclusively) has a weaker and longer bond than X E (see Section III.D.1).…”

“…In addition and with reference to earlier work, which describes the synthesis of a bicyclic piperidone, derived from treating diethyl acetonedicarboxylate, an aldehyde and g-aminobutyraldehyde (79), it is possible to synthesize the bispidine derivative 57 with an unsymmetric substitution pattern (see Chart 6) (80). This finding may be the basis for a whole new series of chiral bispidine ligands.…”

“…Many of the coordinated ligands have a hydrated ketone at C9 [R 2 C À À À ÀO vs. R 2 C(OH) 2 ]. This finding generally is observed when the complex synthesis is not performed in strictly anhydrous conditions (69,82,189). From pK a values, photoelectron spectroscopy, and MO calculations of diazaadamantane derivatives, it was found that ketones lead to a reduction of the nucleophilicities of the aza-groups.…”

“…force-field calculations (42,69,189,201), which indicate that there is basically no strain induced to the ligand upon coordination to metal ions, except for small metal centers (short metal-donor distances, see Section III.D.1). The result is that bispidine ligands quite generally have a preference for large metal ions, which leads to interesting stabilities and selectivities (see Section III.D.2) (69,201).…”

Interpretation and Prediction of Properties of Transition Metal Coordination Compounds

“…An interesting feature is that for the bispidine ligands, depending on the donor groups, various substituents and the coligands, three possible Jahn-Teller isomers have been isolated and fully characterized (elongation along Cu-N7, Cu-N3 or py1-Cu-py2; for the nomenclature, see Scheme 8.1 and structures presented in Figure 8.1) [136,159,160]. In the light of the present chapter, it is of interest to note that ligand-field-based molecular mechanics is able to predict the most stable Jahn-Teller isomer [136], although for the study reviewed here, the structural data are based on X-ray crystallography [161].…”