This paper describes spectral, non-linear optical (NLO),
and biological
activity variation of pyrrole hydrazones as a result of structural
variation. In order to study structure–property variation,
pyrrole hydrazones (
3A
,
3B
, and
3C
) were synthesized in both solid and solution phases. The grinding
solvent-free method becomes rapid, easy, convenient, useful, sustainable,
and eco-friendly green synthesis as compared to the classical solution
phase reactions. The structure of pyrrole hydrazones has been elucidated
by microanalysis and quantum chemical calculations. The intense emission
at λ
em
521 nm (
3A
and
3B
) and 617 nm (
3C
) in the visible (green and orange)
region with Stokes shifts at 195, 160, and 282 nm reveals that the
studied compounds work as good photoluminescent materials. All compounds
show strong n−π* and charge transfer (π–π*)
transitions in the UV–vis region with high extinction coefficients.
In the studied systems (
3A
,
3B
, and
3C
), the orbital overlap between σ(NH–O) →
σ*(NH–O) is found due to intra-molecular charge transfer.
The first hyperpolarizabilities were found to be 48.83 × 10
–30
esu for
3B
and 63.89 × 10
–30
esu for
3C,
showing variation with
structure. Their high values indicate more suitability for NLO application.
Incorporation and/or change in position of electron-withdrawing groups
increase the β
0
values of
3B
and
3C
compared to
3A
. The β value also increases
monotonically as the polarity of the solvents increases. The red shift
in N–H and C=O stretching Fourier-transform infrared
bonds is due to the formation of dimers. The synthesized
3A
,
3B
, and
3C
show good antimicrobial activity
and are predicted to be potential antibacterial and antifungal drugs.
The
3B
has more molar refractivity (122.16 esu) than
3A
and
3C
and correlates well with the calculated
binding affinity and experimental antimicrobial data.