2.6 Summary
35
2.6 Summary
We introduced the aryl gold isocyanide complex 3 appended with a biphenyl moiety to restrict conformational freedom. The addition of various solvents to ground
powder 3 ground afforded eleven types of 3/solvent with different emission properties (λ em,max ranging from 490 to 580 nm). The 3/solvent samples contain eleven
different types of solvent molecules, which are important for their varied emission
properties. This indicates that 3 can be used as an indicator for various volatile
organic molecules, which can be probed by examining the emission properties of
3/solvent. Mechanical stimulation of 3/solvent reactivated the solvent-responsive
properties of 3 through the recovery of the yellow-emitting 3 ground as a solvent-free
amorphous phase. We prepared single crystals of all eleven 3/solvent corresponding
to the powder forms obtained by simple solvent addition and subsequent evaporation.
To the best of our knowledge, 3 is the first luminescent compound that can form a
dozen fully-solved different solid structures with distinct emission properties. Comparison of the single-crystal structures revealed that crystalline structures differed
from each other. We also obtained solvent-free single crystal 3/none. To understand
the structure–property relationships in the single crystals of 3/solvent and 3/none,
we extracted crystallographic factors, i.e., Au···Au distances, π···π stack distances,
and dihedral angles of benzene rings, and plotted them with respect to corresponding λ em,max . Analyses of the crystal structures of 3/solvent indicated that there was
not one specific structure factor that controlled the emission properties of 3/solvent.
Instead, the emission properties might be the result of the combination of several
structure factors. We could not identify simple design guidelines to predict the emission properties of 3 from its crystal structure. However, we found that including a
biphenyl moiety with restricted rotational freedom into gold isocyanide complexes
enhances the ability of the gold complexes to adopt various crystal structures with
different emission properties in response to solvent addition. This finding should be
important for the design of emission-based solvent-responsive materials.
2.7 Experimental Section
2.7.1 General
All commercially available reagents and solvents are of reagent grade and were used
without further purification unless otherwise noted. Solvents for the synthesis were
purchased from commercial suppliers, degassed by three freeze-pump-thaw cycles
and further dried over molecular sieves (4 Å). NMR spectra were recorded on a JEOL
JNM-ECX400P or JNM-ECS400 spectrometer (
1 H: 400 MHz;
13 C: 99.5 MHz) using
tetramethylsilane and CDCl 3 as internal standards, respectively. Emission spectra
were recorded on a Hitachi F-7000 spectrometer. Fluorescence microscopic spectra
35
2.6 Summary
We introduced the aryl gold isocyanide complex 3 appended with a biphenyl moiety to restrict conformational freedom. The addition of various solvents to ground
powder 3 ground afforded eleven types of 3/solvent with different emission properties (λ em,max ranging from 490 to 580 nm). The 3/solvent samples contain eleven
different types of solvent molecules, which are important for their varied emission
properties. This indicates that 3 can be used as an indicator for various volatile
organic molecules, which can be probed by examining the emission properties of
3/solvent. Mechanical stimulation of 3/solvent reactivated the solvent-responsive
properties of 3 through the recovery of the yellow-emitting 3 ground as a solvent-free
amorphous phase. We prepared single crystals of all eleven 3/solvent corresponding
to the powder forms obtained by simple solvent addition and subsequent evaporation.
To the best of our knowledge, 3 is the first luminescent compound that can form a
dozen fully-solved different solid structures with distinct emission properties. Comparison of the single-crystal structures revealed that crystalline structures differed
from each other. We also obtained solvent-free single crystal 3/none. To understand
the structure–property relationships in the single crystals of 3/solvent and 3/none,
we extracted crystallographic factors, i.e., Au···Au distances, π···π stack distances,
and dihedral angles of benzene rings, and plotted them with respect to corresponding λ em,max . Analyses of the crystal structures of 3/solvent indicated that there was
not one specific structure factor that controlled the emission properties of 3/solvent.
Instead, the emission properties might be the result of the combination of several
structure factors. We could not identify simple design guidelines to predict the emission properties of 3 from its crystal structure. However, we found that including a
biphenyl moiety with restricted rotational freedom into gold isocyanide complexes
enhances the ability of the gold complexes to adopt various crystal structures with
different emission properties in response to solvent addition. This finding should be
important for the design of emission-based solvent-responsive materials.
2.7 Experimental Section
2.7.1 General
All commercially available reagents and solvents are of reagent grade and were used
without further purification unless otherwise noted. Solvents for the synthesis were
purchased from commercial suppliers, degassed by three freeze-pump-thaw cycles
and further dried over molecular sieves (4 Å). NMR spectra were recorded on a JEOL
JNM-ECX400P or JNM-ECS400 spectrometer (
1 H: 400 MHz;
13 C: 99.5 MHz) using
tetramethylsilane and CDCl 3 as internal standards, respectively. Emission spectra
were recorded on a Hitachi F-7000 spectrometer. Fluorescence microscopic spectra