Spectrophotometric and spectroscopic studies on charge transfer complexes of the antifungal drug clotrimazole

Peer review under responsibility of Taibah University.

Figures & data

Fig. 1 Chemical structure of clotrimazole.

Table 4 Characteristic peaks of the CLZ and the π-acceptors.

Name of the compound	Characteristic peaks (cm^−1)	Corresponding functional groups
CLZ	3062	Ar-H
	1490	–C=N–
	750	C-Cl
TCE	2270	–C▂N–
	1653	–C=C–
TCNQ	2222	–C▂N–
	1543	–C=C–

Table 5 Infrared frequencies^a (cm⁻¹) and their band assignments^b for the CLZ, free acceptors, and CLZ-TCE and CLZ-TCNQ complexes.

CLZ	TCE	TCNQ	CLZ-TCE	CLZ-TCNQ	Assignments
3062 ms		3049 s	3163 ms	3049 ms	ν (Ar-H)
	2270 s	2222 s	2198 s	2171 ms	ν (C▂N)
	1699 m	1543 s	1575 m	1570 ms	ν (C=C)
1490 s			1489 ms	1444 ms	ν (C=N)
	1145 m		1159 m		ν (C–C)
750 s			754 s	748 s	ν (C-Cl)

a ν – stretching.

b s – strong; m – medium.

Fig. 2 Absorption spectra of (a) CLZ (1000 μg mL⁻¹), (b) CLZ-TCE (35 μg mL⁻¹) and (c) CLZ-TCNQ (25 μg mL⁻¹).

Fig. 3 Probable reaction mechanisms for the formation of the CLZ-TCE and CLZ-TCNQ complexes.

Fig. 4 Effect of solvent on the reaction of CLZ with TCE and TCNQ.

Fig. 5 Continuous variation plots for the CLZ-TCE and CLZ-TCNQ complexes.

Fig. 6 Calibration plot for the analysis of the CLZ by the proposed methods.

Table 1 Spectral data for the analysis of CLZ with the TCE and TCNQ acceptors.

Parameters	CLZ-TCE	CLZ-TCNQ
λmax (nm)	396	842
Beer’s law limits (μg mL^−1)	5–35	1–25
Molar absorptivity (L mol^−1 cm^−1)	0.5724 × 10^4	3.5864 × 10^4
Sandell sensitivity (μg cm^−2)	0.0602	0.0096
Limit of detection^a (μg mL^−1)	0.2271	0.2343
Limit of quantification^a (μg mL^−1)	0.6883	0.7102
Regression equation^b	Y = a + bX	Y = a + bX
Intercept (a)	−0.0262	0.0891
Slope (b)	0.0215	0.0214
Correlation coefficient (r)	0.9994	0.9985

a Calculated according to ICH guidelines.

b Y is the absorbance and X is the concentration of analyte in μg mL⁻¹.

Table 2 Evaluation of the accuracies and precisions of the proposed methods.

Methods	Amount taken (μg mL^−1)	Amount found^a (μg mL^−1)	RE^b (%)	SD^b (μg mL^−1)	RSD^b (%)	Recovery (%)
CLZ-TCE	10	9.95	0.40	0.09	0.98	99.50
	20	20.05	0.25	0.12	0.61	100.05
	30	29.95	0.16	0.13	0.44	99.83
CLZ-TCNQ	5	5.04	0.94	0.09	1.74	100.80
	13	13.05	0.42	0.11	0.88	100.38
	21	20.94	0.29	0.13	0.61	99.71

a Mean value of five determinations.

b RE, relative error; SD, standard deviation; RSD, relative standard deviation.

Table 3 Statistical results from the analysis of the formulations using the proposed methods.

Brand name	Labelled amount (mg)	Amount found^a ± SD
		CLZ-TCE	CLZ-TCNQ
Coniderm	10	10.02 ± 0.14	10.02 ± 0.11
		t-test^b = 1.02	t-test^b = 0.66
		% Rec^c = 100.20	% Rec^c = 100.20
Surfaz	10	10.01 ± 0.13	9.96 ± 0.06
		t-test^b = 0.33	t-test^b = 1.39
		% Rec^c = 100.10	% Rec^c = 99.60

a Mean value of five determinations.

b Theoretical t value at 95% confidence level is 2.77.

c Recovery.

Fig. 7 Infrared spectra of CLZ-TCE.

Fig. 8 Infrared spectra of CLZ-TCNQ.