D

J. Chem. Chem. Eng. 2 (2016) 53-59
doi: 10.17265/1934-7375/2016.02.001

DAVID

PUBLISHINGElectrochemical Tuning by Polarized UV Light Induced
Molecular Orientation of Chiral Salen-type Mn(II) andCo(II) Complexes in an Albumin Matrix
Eirika Tsuda1, Yuya Mitsumoto1, Kazuya Takakura1, Nobumitsu Sunaga1, Takashiro Akitsu1*, Taro Konomi2, andMasahiro Katoh2
1. Department of Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
2. UVSOR, Institute for Molecular Science, 38 Nishigonaka, Myodaiji, Okazaki, Aichi 444-8585, Japan
Abstract: The authors have prepared supramolecular systems as artificial metalloproteins composed of several chiral salen-type
Mn(II) and Co(II) complexes in a HSA (human serum albumin) matrix. The docking was discussed by UV-vis spectral changes
and a ligand-protein docking simulation program. After linearly polarized UV light irradiation, that anisotropy of molecularorientation of the complexes increased was confirmed by polarized IR spectra. The authors have observed that the electrochemical
behavior of the aligned complexes incorporating diphenyl groups in HSA can be tuned without UV radiation damage of HSA higher
structures.
Key words: Redox potential, Schiff base, Mn(II) complex, Co(II) complex, albumin.

1. Introduction
In recent years, metal complex-protein hybridmaterials are attracted attention in view of bio-inspired
catalysis [1] or bioinorganic photochemistry [2]. Thesematerials have high eco-compatible, so are called
artificial metalloenzymes as biohybrid materials,
observed in bioinorganic chemistry and pharmacy
fields and using biocatalysis and homogeneous (chiral)
catalysis [3-5]. The report about the composition withprotein and low molecular like complex was little dueto the difficulty of crystallization of hybrid materials
and the requirement of high technique [6].
Herein, the authors have prepared supramolecularsystems as artificial metalloproteins composed ofseveral chiral salen-type Mn(II) and Co(II) complexes
in a HSA (human serum albumin) matrix [7]. After
linearly polarized UV light irradiation, that anisotropyof molecular orientation of the complexes increased [8]*Corresponding author: Takashiro Akitsu, Ph.D., research
field: inorganic coordination chemistry.

was confirmed by polarized IR spectra [9, 10]. The
authors have observed that the electrochemical
behavior of the aligned complexes incorporating
diphenyl groups in HSA can be tuned without UV
radiation damage of HSA higher structures.

2. Experiments
Chiral Schiff base complexes of (1R,
2R)-enantiomers (Fig. 1) (Mn-diphenyl, Mn-cyclo,
and Co-diphenyl) were reported elsewhere [11-14].
For example, a new complex (Co-cyclo) was preparedand characterized as follows: To a solution of
3,5-dichlorosalicylaldehyde (0.0955 g, 0.500 mmol)
dissolvedinmethanol(50 mL),(1R,2R)-(+)-1,2-diaminocyclohexane (0.0285 g, 0.250mmol) was added dropwise and stirred at 313 K for 2
h to give yellow solution of ligand. Cobalt(II) acetate
tetrahydrate (0.0623 g, 0.25 mmol) was added to theresulting solution to give brown solution of complex.
After stirring for 4.5 h under N2, brown solution was
filtrated to obtain brown precipitates. Yield 0.0696 g

54Electrochemical Tuning by Polarized UV Light Induced Molecular Orientation of Chiral
Salen-type Mn(II) and Co(II) Complexes in an Albumin Matrix(a)

The docking of meal complexes into HSA wasdiscussed by UV-vis spectral changes (30 µM of
metal complexes in 0-8 mg of HSA solutions in pH
5.10 sodium citrate buffer at 273 K) (Fig. 2),
corresponds to Stern-Volmer discussion by fluorescence
spectra [7], and a CCDC GOLD program for ligand(TD-DFT optimized structure)–protein (PDB: 1BM0
crystal structure) docking simulation (Fig. 2). Bothexperimental results and theoretical data suggested
that docking of Co-diphenyl + HSA was madeadequately.
3.2 Irradiation of Polarized UV Light(b)
Fig. 1 Molecular structures of chiral salen-type (a)diphenyl; or (b) cyclo (M = Mn or Co) complexes.

(53.83%). Anal. Calcd. for C20H16Cl4CoN2O2: C,
46.45; H, 3.12; N, 5.42. Found: C, 46.46; H, 3.01; N,
5.24%. IR (KBr (cm-1)): 1,637(C=N). In addition, castfilms for spectral and electrochemical measurements
were prepared [15, 16]. Commercially available HSA(0.0152 g) and acetone solution of the complexes(1 mM) were mixed in sodium citrate buffer (2 mL),and dropped onto a PMMA cast film and dried for 2days at 298 K.

3. Results and Discussions
3.1 Spectral Interpretation and Docking
Absorption of UV light by metal complexes mainly
was attributed to intra-ligand transitions andexperimental UV-vis spectra was reasonably assigned
by TD-DFT calculations with UCAM-B3LYP/6-31G(d)on Gaussian09. Co-cyclo: 221 nm HOMO-1 →LUMO+3,266 nm, HOMO → LUMO+2,278 nm
HOMO-1 → LUMO+1,335 nm HOMO-1 → LUMO;
Co-diphenyl: 242 nm HOMO-5 → LIMO+1,266.78
nm HOMO → LUMO+4,278 nm HOMO-1 →LUMO ( α ), 336 nm HOMO-1 → LUMO ( β ).

Weigert effect by linearly polarized UV light causes
dichroism due to anisotropic aligned metal complexes
in a HSA matrix with photochemical reactions as wellas interaction with highly polar molecules [8]. The
magnitude of polarized light-induced anisotropy was
Co-cyclo > Co-diphenyl > Mn-cyclo > Mn-diphenyl.
The degree of photoinduced optical anisotropy ofangular dependent changes of polarized IR spectra of
C=N bands in metal complexes (1,653 cm-1, 1,642 cm-1,
1,654 cm-1, and 1,652 cm-1 for Mn-diphenyl + HSA,
Mn-cyclo + HSA, Co-diphenyl + HSA, and Co-cyclo+ HSA, respectively) can be described by S and R
parameters (Fig. 3 and Tables 1-4).
Where Aperpendicular and Aparallel values denoteabsorbance measured with the measuring polarizer
parallel (0°) or perpendicular (90°) to electric vectorof irradiation polarized light. The ideal isotropic
system of S = 0 and R = 1 both S and R parameters
are changed as increasing dichroism by molecularalignment [15].
However, even strong synchrotron UV linearlypolarized UV light irradiation (at 260 nm, 318 nm,
and 380 nm of 102 mm2 spot at 10 mW/cm2 generated
with an undulator at IMS UVSOR BL1U [17]) did not
damage higher structure of HSA for Co-diphenyl +HSA or Co-cyclo + HSA. Little changes from theinitial CD spectra in the range of 200-900 nm could beobserved after 1 min, 3 min, and 5 min irradiation.

mical Tuning by Polarizedd UV Light Ind
duced Molecu
ular Orientatiion of ChiralElectrochem
xes in an Albumin Matrix
Salen-type Mn(II) and Co(II) Complex

(a)

(b)

(c)

Fig. 2(d)
Channges of UV-vis spectra by doccking HSA andd (a) Mn-dipheenyl; (b) Co-dip
phenyl; (c) Mnn-cyclo; and (dd) Co-cyclo.

555

56

Electrochem
mical Tuning by Polarizedd UV Light Ind
duced Molecu
ular Orientatiion of Chiral
xes in an Albumin Matrix
Salen-type Mn(II) and Co(II) Complex

((a)
(bb)
diphenyl and HAS;
H(b) Ligannd-protein doccking simulatioon by a GOLD
D
Fig. 3 (a) Changes of UV--vis spectra byy docking Co-dC
+ HSA.
program for Co-diphenyl
Table 1R and
a S parameteers for Mn-dip
phenyl + HSA.

UV irradiattion time /minn.
innitial
U
UV0.5
U
UV1
U
UV3
U
UV5
U
UV10
Table 2R
1.5764844
1.2179633
1.4333777
1.3359055
1.6042877
1.0918333

S
0.1611887
0.0677333
0.1262225
0.1006994
0.1676558
0.0297002

R and
a S parameteers for Mn-dip
phenyl + HSA.

UV irradiattion time /minn.
innitial
U
UV0.5
U
UV1
U
UV3
U
UV5
U
UV10
Table 4

S
0.0741336
0.1894445
0.1240002
0.1451774
0.085915
0.0304996

R and
a S parameteers for Co-diphhenyl + HSA.

UV irradiattion time /minn.
innitial
U
UV0.5
U
UV1
U
UV3
U
UV5
U
UV10
Table 3R
1.2402166
1.701171.42665
1.5094877
1.2819711
1.0943644

R
1.2469855
1.2044199
1.14387
1.2176777
1.1999811
1.1684333

S
0.1611887
0.0677333
0.0457662
0.067655
0.0624994
0.53166

R anda S parameteers for Co-cycllo + HSA.

UV irradiattion time /minn.
innitial
U
UV0.5
U
UV1
U
UV3
U
UV5
U
UV10

R
1.1171811
1.2000799
1.2466877
1.2629766
1.1412544
1.4111566

S = (Aparallel – Aperpendicular)/(2Apeerpendicular + Aparalleel)
R = Aperpendicularr/AparallelS
0.0375992
0.0625223
0.0759881
0.0805994
0.0449667
0.1205333

3.3 Electrochemical EffectThe
T CV meassurements revealed the efffects of UVVlighht for not only metaal complexees but alsoocommplex-HSA hybrids (Fiig. 4). In contrast too
relaatively UV liight-resistant complexes Mn-diphenyll
andd Co-diphenyyl, Mn-cyclo and Co-cycclo exhibiteddCV
V changes aftter UV irradiiation for 10
0 min, whichhmay
y be in agreement with eexpectation basedbon thee
intrra-ligand trannsitions or staable isolationn [18] and O2
oxiddation duringg preparationn from Mn(II)) source [19]]for the analoggous Mn(IIII)-cyclo com
mplexes. Asscom
mplex-HSA hybrids,h
Co-ddiphenyl + HS
SA exhibitedd
littlle CV changes, though oonly Mn-diphhenyl + HSAAexhhibited signifiicant CV chaanges (decreaasing current))
only
y after 1 min polarized UV
V irradiation (Fig. 5).

4. ConclusionCns
Inn conclusioon, the auuthors hav
ve preparedd
supramolecular systems as artificial meetalloproteinsscom
mposed of several chiral salen-type Mn(II) andd
Co((II) complexees in a HSA matrix, and theirtdockinggfeattures were coonfirmed expperimentally. Polarized IR
R
specctra indicatedd that anisotroopic moleculaar orientationnof metal compllexes in HSA has been induced byy
irraadiation linearly polarizeed UV lightt. Excludingg
unstable metal complexes and denying
g irradiationn
dammage of HSA
A, the authorss have successsfully foundd
thatt electrochem
mical tuningg by polarizeed UV lightt

Electrochemical Tuning by Polarized UV Light Induced Molecular Orientation of Chiral
Salen-type Mn(II) and Co(II) Complexes in an Albumin Matrix

57

(a)

(b)

(c)

(d)
Fig. 4 Changes of CV after polarized UV light irradiation for only complex and complex+HSA hybrids for (a) Mn-diphenyl;(b) Co-diphenyl; (c) Mn-cyclo; and (d) Co-cyclo systems.

58Electrochem
mical Tuning by Polarizedd UV Light Ind
duced Molecu
ular Orientatiion of Chiral
xes in an Albumin Matrix
Salen-type Mn(II) and Co(II) Complex

(
(a)
(b)
ngular depend
dence of intensiity of polarizedd IR spectra foor Mn-diphenyyl complex + H
HSA after polarized UV lightt
Fig. 5 (a) An
irradiation. (bb) Changes of CV for Mn-dip
phenyl + HSA after polarized UV light irraadiation.

induced molecularmorientation associatedaw
withperturbationn of hydrogeen bonding electron trannsfer
paths only forf Mn-dipheenyl + HSA forf the first time.
After establiishment of reeaction condittions, the connceptwillbepotentiallyappliedfor
artifficial
metalloproteeins [20] as biofuel cell maaterials [21].

Acknowledgments
Some parrts of this workw
were suppported by JointJ
Studies of ProgramPof Innstitute for Molecular Scieence,
Okazaki, Jaapan, using UVSORUFaccility, Instrum
mentCenter andd Research Centre forr Computatiional
Science. Thhe computatiion was maainly carried out
using the coomputer facillities at Research Institutee forInformation Technology,, Kyushu Uniiversity.

Referencees
[1]
[2]

[3]

[4]

[5]

Ueno, T., and Wattanabe, Y. 2013. Coordination
C
USA: Wiiley.
Chemistrry in Protein Cages.
Stochel, G., Brindell, M.,
M Macyk, W.,
W Stasicka, Z.,, andwski, K. 20099. Bioinorganic Photochemistry.
Szacilow
USA: Wiley.
W
S.-Dagousset, E., Urvooas, A., Chellyy, K., Ghattas,, W.,
R
R. 2014.
2
Marecal, J., Mahy, J., and Ricoux,
HybridBiocatalysts
for“Neocarrzinostatin-baseed
Oxidatioon Reactions.” Dalton
D
Transacctions 43: 8344--54.
Bartok, M.
M 2010. “Uneexpected Inversions in Asymm
metricReactionns: Reactions with Chiral Metal Complexes,
Chiral Organocatalyssts, and Heteerogeneous ChiralCs.”ChemicalReviews110:
1663-705.
Catalyst
Lee, S. J., and Lin, W. 2008. “Chhiral Metallocyycles:
Rationall Synthesis andd Novel Applicaations.” Accounnts ofChemicaal Research 41: 521-37.

[6]

Das, K., Dattta, A., Nandi, S., Mane, S. B.,
B Mondal, S.,,
Massera, C.,, Sinha, C., H
Hung, C. H., Celikboyun,
CP.,,
Cantürk, Z., Garribba,
GE., annd Akitsu, T., 2015.
2“A Ni(II))
Dinuclear Complex Bridgeed by End-on
n Azide-N andd
Phenolate-O Atoms: Spectrral Interpretatioon, Magnetismmand Biologiccal Study.” Inorrganic Chemistry Frontier 2::
749-62.
[7] Hayashi, T.,, and Akitsu, T. 2015. Thrreonine: Foodd
Sources, Funnctions and H
Health Benefitss. USA: Novaa
Science Publishers Inc..
[8] Natansohn, A.,
A and Rochon, P. 2002. “Photoinducedd
Motions in Azo-Containning Polymerrs.” Chemicall
Reviews 102:: 4139-76.
[9] Hicks, M. R.,
R Kowalski, J.., and Rodger, A. 2010. “LDDSpectroscopyy of Natural aand Synthetic Biomaterials.””
Chemical Socciety Reviews 39: 3380-93.
[10] Ivanova, B., and Kovev, T.. 2012. Linearlly Polarized IR
R
Spectroscopyy. USA: CRC Prress.
[11] Akitsu, T., anda Tanaka, R.. 2011. “Polariized Electronicc
and IR Specctra of Hybridd Materials of Chiral Mn(II))
Complexes anda Different T
Types of Photoochromic Dyess
Showing Phootoisomerizationn or Weigert Effect.”
E
CurrenttPhysical Cheemistry 1: 82-9.
[12] Akitsu, T., Taanaka, R., and Y
Yamazaki, A. 2011.
2“Separatee
Observation with Polarized Electronic andd IR Spectra off
Hybrid Materials of Chiral Mn(II) ComplexesC
andd
Azobenzene.”” Journal of Materials Science andd
Engineering A 1: 518-25.
[13] Yoon, D. H., Jamshaid, A., Ito, J., Nakahaara, A., Tanaka,,
D., Akitsu, T.,
T Sekiguchi, S
S., and Shoji, S.. 2014. “Activee
Microdroplett Merging by Hydrodynamic Flow Controll
Using a Pneeumatic Actuattor-assisted Pilllar Structure.””Lab on a Chip
ip 14: 3050-5.
[14] Tanaka, D., Yoon, D. H., Sekiguchi, T., Shoji, S., andd
Akitsu, T. 2014. In Proceedings of the 6th Int. Symp.
Microchem. Microsys-ISMM
M
M.
[15] Yamazaki, A., and Akkitsu, T. 2012. “Polarizedd
Spectroscopyy and Polarized UV Light-indu
uced MolecularrElectrochemical Tuning by Polarized UV Light Induced Molecular Orientation of Chiral
Salen-type Mn(II) and Co(II) Complexes in an Albumin Matrix
Orientation of Chiral Diphenyl SCHIFF Base Ni(II) andCu(II) Complexes and Azobenzene in a PMMA Film.”
RSC Advances 2: 2975-80.
[16] Kominato, C., and Akitsu, T. 2015. “Photoinduced
Molecular Orientation of Catalytic-like Chiral Azo-Schiff
Base Complexes in PMMA or Laccase Matrices.” Lettersin Applied NanoBioSciences 2: 264-70.
[17] Katoh, M. 2015. Light Source in 2014: UVSOR Activity
Report 2014.
[18] Akitsu, T., Takeuchi, Y., and Einaga, Y. 2005. “Diaqua­[(1R,2R)-N,N’-bis-(3,5-di-bromosalicylidene)cyclohexan
e-1,2-diamine- κ 4O,N,N’,O’] Manganese(III)59

Perchlorate Dehydrate.” Acta Crystallographica E 61:
772-4.
[19] Okamoto, Y., Nidaira, K., and Akitsu, T. 2012.
Crystallography: Research, Technology and Applications
USA: Nova Science Publishers Inc..
[20] Tanaka, D., Murakoshi, Y., Tsuda, E., Mitsumoto, Y.,
Yoon, D. H., Sekiguchi, T., Akitsu, T., and Shoji, S. 2015.
In Proceedings of the Transducers 2015 IEEE.
[21] Kurosawa, Y., Tsuda, E., Takase, M., Yoshida, N.,
Takeuchi, Y., Mitsumoto, Y., and Akitsu, T. 2015.
Threonine: Food Sources, Functions and Health Benefits.
USA: Nova Science Publishers Inc..