Anion Effect on the Formation of Zinc-Salicyaldimine Compounds in Neutral and Anionic Complex Forms: Synthesis, Characterization, 1H NMR Studies, and Photophysical Properties

Article abstract of DOI:10.1002/ejic.202100377

Reactions of Zn(BF₄)₂ and ZnCl₂ with a nitrile-functionalized salicyaldimine ligand, 3-(salicylideneimino)benzonitrile (Hsal-3-PhCN), in both 1 : 1 and 1 : 2 stoichiometry of metal-to-ligand, afforded zinc-salicyaldimine compounds [Zn(sal-3-PhCN)₂] (1) and [HNEt₃][Zn(sal-3-PhCN)Cl₂] (2), respectively. Compound 1 is a neutral zinc-salicyaldimine complex, where the Zn(II) center is in a distorted {ZnN₂O₂} tetrahedral geometry, made up of two sal-3-PhCN ligands both in the N,O-chelating mode. Comparably, 2 is an ionic zinc-salicyaldimine compound, where the Zn(II) center is in a distorted {ZnNOCl₂} tetrahedral geometry, made up of one sal-3-PhCN ligand in the N,O-chelating mode and two chloro ligands. The results indicate that neutral and anionic forms of zinc-salicyaldimine complexes would form under the domination of anion with different zinc-binding abilities. ¹H NMR studies indicate different degrees of decomplexation of 2 in different solvents, leading to a dynamic equilibrium between the zinc-salicyaldimine complex form and the neutral form of salicyaldimine ligand. This is achieved by proton transfer and interpreted by the hydrogen-bonding properties of the solvents. Photophysical studies reveal that Hsal-3-PhCN exhibited weak yellow fluorescence (λ_em=554 nm) while 1 and 2 emitted strong blue (λ_em=472 nm) and green (λ_em=504 nm) fluorescence, respectively, in solid-state, and in comparison, much weaker emissions in solution phases.

Full text of DOI:10.1002/ejic.202100377

Full Papers
doi.org/10.1002/ejic.202100377
Anion Effect on the Formation of Zinc-Salicyaldimine
Compounds in Neutral and Anionic Complex Forms:
Synthesis, Characterization, 1H NMR Studies, and
Photophysical Properties
Meng-Jung Tsai+,[a] Yo-Ting Su+,[a] and Jing-Yun Wu*[a]
Reactions of Zn(BF4)2 and ZnCl2 with a nitrile-functionalized
salicyaldimine ligand, 3-(salicylideneimino)benzonitrile (Hsal-3-
PhCN), in both 1:1 and 1:2 stoichiometry of metal-to-ligand,
afforded zinc-salicyaldimine compounds [Zn(sal-3-PhCN)2] (1)
and [HNEt3][Zn(sal-3-PhCN)Cl2] (2), respectively. Compound 1 is
a neutral zinc-salicyaldimine complex, where the Zn(II) center is
in a distorted {ZnN2O2} tetrahedral geometry, made up of two
sal-3-PhCN ligands both in the N,O-chelating mode. Compara-
bly, 2 is an ionic zinc-salicyaldimine compound, where the Zn(II)
center is in a distorted {ZnNOCl2} tetrahedral geometry, made
up of one sal-3-PhCN ligand in the N,O-chelating mode and two
chloro ligands. The results indicate that neutral and anionic
forms of zinc-salicyaldimine complexes would form under the
domination of anion with different zinc-binding abilities. 1H
NMR studies indicate different degrees of decomplexation of 2
in different solvents, leading to a dynamic equilibrium between
the zinc-salicyaldimine complex form and the neutral form of
salicyaldimine ligand. This is achieved by proton transfer and
interpreted by the hydrogen-bonding properties of the sol-
vents. Photophysical studies reveal that Hsal-3-PhCN exhibited
weak yellow fluorescence (λem =554 nm) while 1 and 2 emitted
strong blue (λem =472 nm) and green (λem =504 nm)
fluorescence, respectively, in solid-state, and in comparison,
much weaker emissions in solution phases.
Introduction
metries that are able to modulate the properties of coordina-
tion environments. Further, zinc(II) ion is optical-inactive
showing no essential d–d electronic transitions. Therefore,
fluorescence-responsive zinc complexes are encouraged to
have the lowest energy excited states mainly originated from a
ligand-centered charge transfer (LCT) (or intraligand charge
transfer, ILCT) and/or ligand-to-ligand charge transfer (LLCT),
rarely arose from ligand-to-metal charge transfer (LMCT) states
involving s or p empty orbitals of the metal.[19,20]
Salicyaldimines, also called salicylaldehyde Schiff bases or
imine-phenol Schiff bases,[1] are half-salen-type ligands showing
coordinate properties similar to that of 8-hydroxyquinoline
since those ligands usually demonstrate the chelation of imine
nitrogen atom and phenoxo oxygen atom to metal center,[2]
i.e., a N,O-chelating systems in coordination chemistry. In
addition, salicyaldimines and 8-hydroxyquinoline have similar
delocalized π-systems which result in an analogy between the
emission behaviors of both types of compounds.[2,3] Therefore,
metal complexes of salicyaldimines have been previously
studied about their structures, properties, and reactions and
have important contributions to the development of
Zinc(II) complexes of salicyaldimines are expected to exhibit
not only good fluorescence properties but also fluorescence
tuning both in intensity and/or in wavelength,[20,21] which are
relevant to the substitution of ligands and the coordination
pattern imposed by the ligands.[20,22–25] Therefore, zinc-salicyaldi-
mine complexes have showed potential as light-emitting
layers[22,26,27] and fluorescent sensors.[28,29] For example, the chiral
Zn(II) complex [Zn(HL1)Cl2] (HL1 =4-methyl-2,6-di[(S)-(+)-1-
phenylethyliminomethyl] phenol), where the zinc(II) center is
four-coordinated with one phenolato oxygen and one imine
nitrogen from the ligand HL1, and two chloride ligands in a
distorted tetrahedral geometry, self-assembles via CÀ H···Cl
hydrogen bonds into supramolecular left-handed helices and
exhibits emission properties at room temperature.[21] The
binuclear complex [Zn2(L2)2] (H2L2 =N,N’-bis(2-hydroxybenzili-
dene)-2,4,6-trimethylbenzene-1,3-diamine), where the zinc(II)
center is coordinated by phenolato oxygen and imine nitrogen
from two ligands leading to a distorted tetrahedral geometry,
catalysis,[4,5]
magnetism,[6,7]
luminescence,[8–10]
biological
activities,[11,12] molecular architectures,[13–15] and materials
chemistry.
Zinc is recognized as one of the most important transition-
metal ions in the human body, where it dominates multiple
biological functions.[16–18] As a closed shell d10 transition-metal
ion, zinc(II) ion lacks ligand field stabilization energy and thus
forms complexes of various coordination numbers and geo-
[a] Dr. M.-J. Tsai,+ Y.-T. Su,+ Prof. Dr. J.-Y. Wu
Department of Applied Chemistry
National Chi Nan University,
Nantou 545, Taiwan
E-mail: jyunwu@ncnu.edu.tw
http://ibestpark.ito.tw/doac/member-detail/16_5/
could act as a fluorescent probe for selective detection of Cu2+
Ag+ ions under aqueous conditions.[10]
/
[+] These authors contributed equally to this paper.
In this paper, we report two zinc-salicyaldimine compounds
1 and 2 from the complexation reactions of a nitrile-functional-
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/ejic.202100377
Eur. J. Inorg. Chem. 2021, 1–10
1
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100377
ized salicyaldimine ligand, namely 3-(salicylideneimino)
molecualr structure of Hsal-3-PhCN is further confirmed by
single-crystal X-ray diffraction analysis, showing identical results
as literature report.[30]
benzonitrile (Hsal-3-PhCN), and zinc salts of tetrafluoroborate
À
(BF4 ) and chloride (ClÀ ), respectively. Spectroscopic studies and
solid-state structure analysis indicated that compound 1 has a
neutral ML2 type zinc-salicyaldimine structure while 2 reveals an
anionic ML type zinc-salicyaldimine structure. Anions of starting
metal salts were found to be responsible for forming zinc-
salicyaldimine structures in the neutral ML2 and anionic ML
Synthesis and Characterization of Zinc-Salicyaldimine
Compounds
1
types. Further, H NMR spectroscopy confirmed that ionic zinc-
The complexation reactions of Zn(BF4)2 and Hsal-3-PhCN with
1:1 or 1:2 stoichiometry of metal-to-ligand in the presence of
several drops of triethylamine (NEt3) in a tetrahydrofuran (THF)
À CH3OH solution yielded a ML2-type zinc-salicyaldimine com-
pound formulated as [Zn(sal-3-PhCN)2] (1), as shown in
Scheme 1. When the same reactions were carried out by using
ZnCl2 instead of Zn(BF4)2, a ML-type ionic zinc-salicyaldimine
compound formulated as [HNEt3][Zn(sal-3-PhCN)Cl2] (2) was
formed. The infrared spectra showed the strong νC=N stretching
band occurring at 1608 cmÀ 1 for 1 and 1610 cmÀ 1 for 2
(Figure S3), both of which are shifted towards lower wave-
numbers compared to that of the free Hsal-3-PhCN ligand
(1614 cmÀ 1), indication of coordination of the azomethine
nitrogen atoms with the zinc centers. Noteworthy, 1H NMR
spectroscopy clearly indicated that stoichiometry of metal-to-
ligand has no influence while anion shows domination on the
formation of ML2 or ML type zinc-salicyaldimine compounds
salicyaldimine compound 2 displayed solvent-dependent de-
complexation, leading to a dynamic equilibrium between the
zinc-salicyaldimine complex form and the neutral form of
salicyaldimine ligand. In addition, the photoluminescent proper-
ties of Hsal-3-PhCN ligand and zinc-salicyaldimine compounds 1
and 2 were investigated.
Results and Discussion
Synthesis and Characterization of Salicyaldimine Ligand
The nitrile-functionalized salicyaldimine ligand, abbreviated as
Hsal-3-PhCN, was synthesized by one-pot aldehyde-amine
condensation reaction of salicylaldehyde and 3-aminobenzoni-
trile with a 1:1 molar ratio in methanol (CH3OH) at room
temperature, as shown in Scheme S1, with an excellent yield
and high purity. 1H NMR spectroscopy indicates that the
azomethine proton (À CH=NÀ ) signal at δ=8.99 ppm and the
phenol proton signal at δ=12.52 ppm were clearly detectable
in deuterated dimethylsulfoxide (DMSO-d6) solvent (Figure S1).
Mass spectroscopy exhibits an intense major peak at m/z=
223.046 (Figure S2), corresponsing to the molecular ion of [Hsal-
3-PhCN+H]+. Furhter, the infrared spectrum shows that the
most diagnostic absorption bands are the C�N and the C=N
stretching modes, occurring at 2226 and 1614 cmÀ 1, respec-
tively (Figure S3). All of these spectroscopic observations
confirm the Schiff base condensation reaction. In addition, the
1
(Figure 1 and Figures S6–S9). The H NMR spectra of ML2-type
zinc-salicyaldimine compound 1 in DMSO-d6 showed a set of
remarkably sharp signals, for which the phenol proton for free
Hsal-3-PhCN at δ=12.52 ppm disappeared whereas the azome-
thine proton showed a large upfield shift from δ=8.99 ppm for
free Hsal-3-PhCN to δ=8.55 ppm for 1. On the other hand, the
1H NMR spectra of ML-type ionic zinc-salicyaldimine compound
2 in DMSO-d6 clearly demonstrated two sets of signals in the
aromatic region and one set of signals in the aliphatic region
(Figures S8 and S9). In the aromatic region, the two sets signals
can be well-resolved to be one set of zinc-salicyaldimine
complex form and one set of neutral form of Hsal-3-PhCN
Scheme 1. Synthesis of 1 and 2
Eur. J. Inorg. Chem. 2021, 1–10
www.eurjic.org
2
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100377
Figure 1. The aromatic region of 1H NMR spectra of [Zn(sal-3-PhCN)2] (1) obtained from the complexation of Zn(BF4)2 and Hsal-3-PhCN with a) 1:2 and b) 1:1
stoichiometry of metal-to-ligand, c) Hsal-3-PhCN, and [HNEt3][Zn(sal-3-PhCN)Cl2] (2) obtained from the complexation of ZnCl2 and Hsal-3-PhCN with d) 1:2 and
e) 1:1 stoichiometry of metal-to-ligand in DMSO-d6 at room temperature. In e), soild square (&) and solid circle (*) symbols represent the two sets of signals
assigning to the neutral Hsal-3-PhCN ligand and the anionic complex part, [Zn(sal-3-PhCN)Cl2]À , of 2, respectively.
ligand (Figure 1). In the aliphatic region, one quartet resonace
signal at δ=2.90 ppm and one triplet resonace signal at δ=
+
1.10 ppm would be assigned to the methylene (HN(CH2CH3)3
and methyl (HN(CH2CH3)3
)
+
) protons, respectively, of the
triethylammonium (HNEt3+) cation of 2. However, it is of
particular note that the set of signals for the neutral form of
1
salicyaldimine ligand always appeared in the H NMR spectra of
1
2 in several independent H NMR measurements, even dissolv-
ing the crystalline samples. The simultaneous existence of both
the zinc-salicyaldimine complex form and the neutral form of
salicyaldimine ligand in solution reasonably implies the pres-
ence of a dynamic equilibrium between decomplxation and
recomplexation, which can be probably processed through
proton transfer between the triethylammonium cations and the
phenoxo groups.[23,31] Similar phenomena have also been
observed for a series of ionic zinc-salicyaldimine analogues,
[HNEt3][Zn(salicyaldimine)Cl2] (salicyaldimine=4-(salicylidenei-
mino)benzonitrile, 4-(5’-chlorosalicylideneimino)benzonitrile, 4-
Figure 2. ORTEP plot of 1. Displacement ellipsoids are drawn at the 30%
probability level.
(5’-bromorosalicylideneimino)benzonitrile,
and
4-(5’-meth-
oxysalicylideneimino)benzonitrile), which showed remarkable
concentration-, solvent-, and substitutent-dependent decom-
plxation/recomplexation equilibria in solution phases.[23]
2.0162(17) Å (Table S1). The C=Nimino bond lengths are C7À N1=
1.307(3) Å and C21À N3=1.308(3) Å and the C�Nnitrile bond
lengths are C14À N2=1.147(3) Å and C28À N4=1.144(3) Å,
referring to typical double bond and triple bond, respectively.
Of particular note, the C=Nimino bond lengths are somewhat
longer than that (1.277 (4) Å)[30] for free Hsal-3-PhCN ligand, as a
result of Zn coordination that causes significant reduction of
C=N bond order. The two chelating sal-3-PhCN ligands show
Crystal Structure of [Zn(sal-3-PhCN)2] (1)
Single-crystal X-ray structure analysis indicated that 1 crystal-
�
lized in triclinic space group P1. The asymmetric unit contains
one Zn(II) center and two sal-3-PhCN ligands. The Zn(II) center
is coordinated by two sal-3-PhCN ligands both in the N,O-
chelating mode, giving rise to a distorted tetrahedral geometry
(Figure 2). The ZnÀ Ophenoxo bond lengths are Zn1À O1=
1.9195(13) Å and Zn1À O2=1.9125(14) Å, and the ZnÀ Nimino
°
the bite angles of O1À Zn1À N1=95.83(6) and O2À Zn1À N3=
°
96.84(6) . The dihedral angles between the benzonitrile phenyl
ring and the salicyaldimine phenyl ring of the same sal-3-PhCN
°
bond lengths are Zn1À N1=2.0151(17)
Å
and Zn1À N3=
ligand are 10.30 and 5.66 . Zinc-salicyaldimine analogues of
Eur. J. Inorg. Chem. 2021, 1–10
www.eurjic.org
3
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100377
[Zn(salicyaldimine)2] structure have also been observed, where
salicyaldimine=salicylidene-aniline, salicylidene-p-meth-
with moderate NÀ H···Cl hydrogen-bonding interaction between
the triethylammonium proton and the chloro ligand, with the
N···Cl distance of 3.199(2) Å for N3À H101···Cl1 and 3.210(2) Å
for N6À H102···Cl4#1 (#1=1+x, y, z) (Table S3). Of note, ML-
ylaniline, salicylidene-p-methoxyaniline, salicylidene-p-cyanoa-
niline, salicylidene(4-dimethylamino)aniline.[22,27,32] A comparison
with relevant crystallographic structural data reported in the
literature on analogous tetrahedral [Zn(salicyaldimine)2] com-
plexes are provided in Table S2.
type
(salicyaldimine)Cl2]
benzonitrile, 4-(5’-chlorosalicylideneimino)benzonitrile, 4-(5’-
bromorosalicylideneimino)benzonitrile, and 4-(5’-meth-
ionic
zinc-salicyaldimine
analogues,
[HNEt3][Zn-
(salicyaldimine=4-(salicylideneimino)
oxysalicylideneimino)benzonitrile) have been documented.[23]
However, these zinc-salicyaldimine analogues showed that the
hydrogen-bonding interaction is formed between the triethy-
lammonium proton of the [HNEt3]+ cation and the phenoxo
oxygen of the [Zn(salicyaldimine)Cl2]À anion; this shows remark-
able difference from that observed in 2.
Crystal Structure of [HNEt3][Zn(sal-3-PhCN)Cl2] (2)
Single-crystal X-ray structure analysis indicated that 2 crystal-
lized in monoclinic space group P21/c. The asymmetric unit
À
consists of two distinct [Zn(sal-3-PhCN)Cl2] anions associated
two distinct triethylammonium cations, [HNEt3]+, as counter-
part. Each Zn(II) center is coordinated by one sal-3-PhCN ligand
in the N,O-chelating mode and two Cl ligands, giving rise to a
distorted tetrahedral geometry (Figure 3 and Figure S14). The
ZnÀ Ophenoxo bond lengths are Zn1À O1=1.9171(15) Å and
Zn2À O2=1.9220(13) Å, the ZnÀ Nimino bond lengths are
Zn1À N1=2.0337(15) Å and Zn2À N4=2.0138(15) Å, and the
ZnÀ Cl bond lengths are Zn1À Cl1=2.2830(5), Zn1À Cl2=
2.2324(5), Zn2À Cl3=2.2419(5), and Zn2À Cl4=2.2698(5) Å (Ta-
ble S1). The C=Nimino bond lengths are typical double bond,
where C7À N1 bond length is 1.300(2) Å and C27À N4 bond
length is 1.302(2) Å, both of which are similar to those in 1 but
somewhat longer than that (1.277 (4) Å)[30] in free Hsal-3-PhCN
ligand due to Zn coordination induced bond order reduction.
The C�Nnitrile bond lengths are typical triple bond, where
C14À N2 bond length is 1.138(3) Å and C34À N5 bond length is
1.143(3) Å. The two chelating sal-3-PhCN ligands show the bite
1H NMR Studies of 2
In order to investigate the influence of solvent on the
decomplxation/recomplexation properties of 2, the 1H NMR
spectra in a series of deuterated solvents including DMSO-d6,
CD2Cl2, acetone-d6, CD3CN, and CD3OD were recorded at a
concentration of approaximately 1.0×10À 2 M (Figure 4 and
Figures S9–S13). As a representative, the degree of decomplxa-
tion of 2 is influenced by used solvents, which can be addressed
in terms of the dissociation ratio (RD) parameter calculated from
the equation:
RD ¼
ICH¼NðHsal À 3 À PhCNÞ
ICH¼NðHsal À 3 À PhCNÞ þ ICH¼Nð½Znðsal À 3 À PhCNÞCl2�À Þ
�100
°
°
angles of O1À Zn1À N1=96.96(6) and O2À Zn2À N4=97.57(6) .
The dihedral angles between the benzonitrile phenyl ring and
the salicyaldimine phenyl ring of the same sal-3-PhCN ligand
where ICH=N(Hsal-3-PhCN) and ICH=N([Zn(sal-3-PhCN)Cl2]À ) are the
relative integrated areas of the azomethine proton signal of the
neutral ligand form and the complex form, respectively.
Accordingly, the RD values in these deuterated solvents are
given in a trend as CD2Cl2 (RD =51.7)>DMSO-d6 (RD =25.4)>
acetone-d6 (RD =7.4)~CD3CN (RD =5.7)>CD3OD (RD = ~0), con-
firming the strong impact of solvent on the decomplxation of 2.
Generally, solvent polarity, i.e., the ability of the solvent to
take part in strong intermolecular interactions with other like
molecules, is usually to address the influence of solvent
strength.[33] However, this seems not to be the domination for
the decomplxation of 2 since that the given trend of polarity
parameters of CH3OH (P’=6.6)>DMSO (P’=6.5)>CH3CN (P’=
6.2)>acetone (P’=5.4)>CH2Cl2 (P’=3.4) is not consistent with
the RD trend. On the other hand, it is noted that the hydrogen-
bonding properties of the solvents may be responsible for the
decomplxation of 2. The greatest decomplexation occurred
when dissolving 2 in CH2Cl2 that has no obvious H-acceptor and
H-donor characteristics, followed in DMSO, acetone, and CH3CN,
that have weak to moderate H-acceptor but no H-donor
characteristics, and the least decomplexation feature was
observed when dissolving 2 in CH3OH that is a good H-acceptor
and H-donor solvent. This makes sense because proton transfer
might be facilitated when hydrogen bonds formed directly
°
are 23.83 and 36.86 for the one chelating to Zn(1) and Zn(2),
respectively. The [HNEt3]+ cation and the [Zn(sal-3-PhCN)Cl2]2À
anion attract each other through electrostatic force associated
Figure 3. ORTEP plot of one of the two crystallographic distinct molecules in
2. Displacement ellipsoids are drawn at the 30% probability level. Empty
dashed line represents the NÀ H···Cl hydrogen bond.
Eur. J. Inorg. Chem. 2021, 1–10
www.eurjic.org
4
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100377
Figure 4. 1H NMR spectra of [HNEt3][Zn(sal-3-PhCN)Cl2] (2) in various deuterated solvents with a concentration of approaximately 1.0×10À 2 M at room
temperature. Solid square (&) and solid circle (*) symbols indicate the azomethine proton signals of the neutral ligand form of Hsal-3-PhCN and the complex
form of [Zn(sal-3-PhCN)Cl2]À , respectively.
between the triethylammonium cations and the phenolato
groups of the sal-3-PhCN ligand of the [Zn(sal-3-PhCN)Cl2]À
anions in CH2Cl2 and thus resulted in a high degree of
decomplexation. Comparably, when the triethylammonium
cations and the [Zn(sal-3-PhCN)Cl2]À anions both were sur-
rounded by H-acceptor and/or H-donor solvents such as DMSO,
acetone, CH3CN, and especially CH3OH, proton transfer might
be inhibited and thus the complex form of [Zn(sal-3-PhCN)Cl2]À
was retained.
CH2Cl2. Similar to RD value, the large Kdecplx value indicates the
high degree of decomplexation of 2 in solution phase.
Accordingly, the degree of decomplexation of 2 in varied
solvents is in the order CH2Cl2 >DMSO>acetone~CH3CN>
CH3OH. Table 1 summarizes the analyses of dissociation ratios
and decomplexation constants for 2 in various solvents.
Photophysical Properties
Further, a simple assumption is that the decomplexation of
2 gives a neutral Hsal-3-PhCN ligand and a ZnCl2 ·NEt3 species
in equal equivalent as shown below:
The optical absorption and fluorescence excitation spectra for
Hsal-3-PhCN, 1, and 2 were investigated in various solvents and
in solid-state at room temperature (Figure 5 and Figure S15).
The relvant photophysical data are provided in Table 2. The UV-
Vis absorption spectra of Hsal-3-PhCN and zinc-salicyaldimine
compounds 1 and 2 in solution phases including CH2Cl2, DMSO,
acetone, CH3CN, and CH3OH with a concentration of 1.0×
10À 4 M exhibited no significant solvatochromism. The UV-Vis
absorption spectra of Hsal-3-PhCN recorded in CH2Cl2, DMSO,
CH3CN, and CH3OH all displayed two strong absorption bands
at about 275 and 341 nm together with a relative weak
absorption band at about 318 nm (Figure 5a). These bands can
mostly be ascribed to the typical electronic transition of an
aromatic ring (π!π*) and À C=NÀ conjugate system (π!π* and
n!π*) in a Schiff molecule.[10,23,25,34,35] Acetone has strong
interference in 250–325 nm, hiding the high-energy absorption
The decomplxation constant (Kdecplx) for the dynamic decom-
plxation/recomplexation equilibrium can be determined using
the equation:
½Hsal À 3 À PhCN� � ½ZnCl2�NEt3�
Kdecplx
¼
½½HNEt3�½Znðsal À 3 À PhCNLÞCl2��
This equation can also be expressed in terms of the
dissociation ratio parameter, RD, and the initial concentration of
2, [[HNEt3][Zn(sal-3-PhCN)Cl2]]0, as
2
ðRDÞ
Kdecplx
¼
� ½½HNEt3�½Znðsal À 3 À PhCNÞCl2��0
100 � ð100 À RDÞ
Table 1. Dissociation ratios (RD) and decomplexation constants (Kdecplx) of
zinc-salicyaldimine compound 2 in various solvents at room temperature
with an initial concentration of 1.0×10À 2 M.
In this study, the initial concentration of [HNEt3][Zn(sal-3-
PhCN)Cl2] is set in 1.0×10À 2 M. As a result, the Kdecplx values are
calculated to be ~0 M in CH3OH, 3.45×10À 5 M in CH3CN, 5.91×
10À 5 M in acetone, 8.65×10À 4 M in DMSO, and 5.53×10À 3 M in
CH3OH CH3CN
Acetone
DMSO
CH2Cl2
RD
decplx (M)
~0
~0
5.7
7.4
25.4
51.7
K
3.45×10À 5 5.91×10À 5 8.65×10À 4 5.53×10À 3
Eur. J. Inorg. Chem. 2021, 1–10
www.eurjic.org
5
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100377
acetone showed only the low-energy absorption band in the
visible wavelength region due to the solvent interference in the
UV wavelength region. In some cases, one further ILCT
transition (n!π*) was also observed as a shoulder band for 1 in
CH2Cl2 (ca. 337 nm) and for 2 in CH2Cl2 (ca. 343 nm) and DMSO
(ca. 337 nm). However, the spectra of the zinc-salicyaldimine
compounds taken in in five different solvents (CH2Cl2, DMSO,
acetone, CH3CN, and CH3OH) do not exhibit any significant
solvatochromism. For Hsal-3-PhCN, 1, and 2, their solid-state
excitation spectra are very similar, with two bands at around
280 and 366 nm, and a further band at 452 nm for 2 (Fig-
ure S15).
The photoluminescence spectra and quantum yields (ΦPL)
of Hsal-3-PhCN and zinc-salicyaldimine compounds 1 and 2
have also been investigated in solid-state and in solution
phases of various solvents (Figure 6). Upon excitation, Hsal-3-
PhCN exhibited weak yellow-light fluorescence centered at
λem =554 nm in solid-state but silent fluorescence in solution
phases (Figure 6a and Figure 6d). The quantum yields of Hsal-3-
PhCN in solid-state and in various solution phases were
measured to be 0.096 and 0.0004–0.001, respectively (Table 2).
This property shows similarity with other salicyaldimine deriva-
tives and can be interpreted by a photoinduced electron
transfer (PET) process due to the presence of lone pair of
electrons of the donor atom in the salicyaldimine ligand, thus
quenching
the
fluorescence
of
the
salicyaldimine
compounds.[36–38] On the other hand, zinc-salicyaldimine com-
pounds 1 and 2 emitted strong blue-light (λem =472 nm, ΦPL =
0.255) and green-light (λem =504 nm, ΦPL =0.385) fluorescence,
respectively, in solid-state (Figures 6b–6d), which are tentatively
ascribed to ILCT emission of the compounds[31,36,39] due to that
divalent zinc ion with stable d10 electronic configuration is
redox-inert to prevent metal-based charge transfers.[40] In
comparison to Hsal-3-PhCN, the fluorescence emissions for 1
and 2 are blue-shifted by 82 and 50 nm, respectively, in
wavelength and enhanced by about 2.7 and 4.0 times,
respectively, in quantum yield. Upon complexation, an excitate
state centered on the bonded salicyaldimine ligand might be
lowering in energy, resulting in a qualitative blue shift of the
fluorescence emission maximum.[20,21,39] Meanwhile, complex
formation with the chelation of azomethine nitrogen and
phenolate oxygen atoms causes chelation enhanced
fluorescence (CHEF) effect[38,41,42] and inhibits the C=N
isomerization.[43–46] This significantly not only reduces the PET
quenching effect but also increases structure rigidity to reduce
the probability of non-radiative relaxation process by vibra-
tional and rotational decay. As a result, the fluorescent intensity
increases greatly. In solution phases, zinc-salicyaldimine com-
pounds 1 and 2 showed weak fluorescence centered at 470–
508 and 500–508 nm, respectively (Figure 6b and Figure 6c).
The quantum yields of 1 and 2 in various solution phases were
measured to be 0.023–0.070 and 0.022–0.098, respectively,
which are much lower than that in solid-state.
Figure 5. UV-Vis absorption spectra of a) Hsal-3-PhCN, b) 1, and c) 2 in
various solvents (1.0×10À 4 M) at room temperature.
bands of about 275 and 318 nm and leaving only the low-
energy absorption band of about 341 nm for Hsal-3-PhCN. For
zinc-salicyaldimine compounds 1 and 2, their UV-Vis absorption
spectra showed an intense absorption band in the UV wave-
length region of 280–293 nm and
a moderately intense
absorption band in the visible wavelength region of 390–
407 nm (Figures 5b–5c). With reference to those for Hsal-3-
PhCN, the high-energy absorption bands are originated from
ILCT transitions (π!π*) whereas the low-energy absorption
bands, absent in the absorption spectra of free ligand, are
assigned to involve both the ligand and the metal center,
probably due to the coordination of C=N to the metal, showing
the d10(Zn)!π*(azomethine) character.[35,36] Again, 1 and 2 in
Eur. J. Inorg. Chem. 2021, 1–10
www.eurjic.org
6
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100377
Table 2. Photophysical data for Hsal-3-PhCN, 1, and 2 in various solvents (1.0×10À 4 M) and in solid-state at room temperature.
Compound
Medium
Absorption/excitation
Fluorescence
λmax [nm] (λex [nm])
λmax [nm] (ɛ [MÀ 1 cmÀ 1])
ΦPL
Hsal-3-PhCN
CH2Cl2
DMSO
acetone
CH3CN
CH3OH
solid-state
CH2Cl2
DMSO
acetone
CH3CN
CH3OH
solid-state
CH2Cl2
273 (29600), 318 (19700), 342 (21200)
277 (26800), 321 (20200), 340 (21800)
341 (27500)
273 (32500), 315 (21800), 341 (23300)
273 (31500), 316 (20800), 341 (22200)
282, 368
289 (34100), 337sh (18600), 404 (10000)
286 (23300), 392 (16800)
403 (27900)
293 (30100), 400 (18300)
293 (36400), 392 (19700)
280, 366
280 (30800), 343 (19000), 399 (6600)
285 (29400), 337sh (19400), 400 (7500)
407 (23200)
287 (26700), 404 (18600)
290 (31000), 390 (15900)
274, 366, 452
n.d. (340)
n.d. (340)
n.d. (340)
n.d. (340)
n.d. (340)
554 (350)
508 (345)
508 (390)
470 (400)
506 (400)
500 (390)
472 (350)
502 (405)
506 (405)
508 (400)
500 (400)
500 (390)
504 (350)
0.0004
0.0006
0.001
0.0005
0.0007
0.096
0.045
0.045
0.025
0.043
0.070
0.255
0.062
0.074
0.022
0.067
0.098
0.385
1
2
DMSO
acetone
CH3CN
CH3OH
solid-state
Figure 6. Photoluminescence spectra of a) Hsal-3-PhCN, b) 1, and c) 2 in solid-state and in various solvents (1.0×10À 4 M) at room temperature. d) Photos of
solid samples of Hsal-3-PhCN, 1, and 2 with illumination of sunlight and UV light of 365 nm.
Conclusion
zinc-salicyaldimine complex form and the neutral form of
salicyaldimine ligand, as a result of proton transfer induced
decomplexation and recomplexation of 2 between the proto-
nated triethylammonium cations and the phenolato groups. In
particular the degree of decomplexation of 2 seems to be
significantly affected by the hydrogen-bonding properties of
the solvents. On the other hand, zinc-salicyaldimine compounds
1 and 2 in comparison to free salicyaldimine ligand both exhibit
Two zinc-salicyaldimine compounds have been successfully
synthesized and structurally characterized. Compound [Zn(sal-3-
PhCN)2] (1) with a ML2 complex form was obtained using
Zn(BF4)2 as metal source while compound [HNEt3][Zn(sal-3-
PhCN)Cl2] (2) with a ML complex form was prepared using ZnCl2
as reagent. Varying stoichiomentry of metal-to-ligand from 1:1
to 1:2 did not affect the formation of 1 and 2. Therefore, anion
instead of metal-to-ligand molar ratio herein shows main
domination on the formation of zinc-salicyaldimine compounds
in ML2 and ML complex forms. The 1H NMR studies of 2 in
various solvents indicate that there is equilibrium between the
strong blue and green fluorescence emissions centered at λem
=
472 and λem =504 nm, respectively, in solid-state and in solution
phases. The obtained compounds broaden an increasing family
of luminescent zinc-salicyaldimine complexes.
Eur. J. Inorg. Chem. 2021, 1–10
www.eurjic.org
7
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100377
1.8 Hz, 1H), 6.62 (d, J=8.7 Hz, 1H), 6.53 (t, J=7.2 Hz, 1H), 2.90 (q,
Experimental Section
Materials and instrumentation. Chemical reagents were purchased
J=7.2 Hz, 6H), 1.09 (t, J=7.2 Hz, 9H). MS (MALDI-TOF+): m/z
457.223 [M]+ (459.73). IR (KBr pellet, cmÀ 1): 2230 (νC�N), 1610 (νC=N).
Anal. calcd for C20H25Cl2N3OZn: C, 52.25; H, 5.48; N, 9.14%. Found: C,
1
commercially and used as received without further purification. H
NMR spectra were recorded on a Bruker AMX-300 Solution-NMR
spectrometer. Chemical shifts are reported in parts per million
(ppm) with reference to the residual protons of the deuterated
solvent. Coupling constants are reported in hertz (Hz). Mass spectra
were recorded with a Bruker Daltonics flexAnalysis matrix-assisted
laser desorption/ionization time of flight (MALDI-TOF) mass spec-
trometer. Infrared (IR) spectra were recorded on a Perkin-Elmer RX1
Fourier transform infrared spectrometer using KBr discs in the
4000–500 cmÀ 1 region. Elemental analyses were performed on an
Elementar Vario EL III analytical instrument. UV-vis absorption
spectra were recorded on a JASCO V-750 UV/VIS spectrophotom-
eter. Fluorescence spectra were recorded on a Hitachi F7000
fluorescence spectrophotometer. Absolute luminescence quantum
yield measurements of powders and liquid samples were con-
ducted through the use of an integrating sphere. Melting points
were measeurd on a Fargo MP-1D melting point apparatus.
°
51.94; H, 5.35; N, 9.26%. Melting point: 189–191 C. Yellow prismatic
single crystals suitable for X-ray diffraction were obtained after one
week by slow diffusion of ether into the methanol solution of
[HNEt3][Zn(sal-3-PhCN)Cl2] (2) at room temperature.
Single-crystal structure determination. Single-crystal X-ray diffraction
data collections were performed by using a Bruker Smart CCD
diffractometer for 1 and a Bruker D8 Venture diffractometer for 2.
The radiation used was graphite monochromated Mo Kα radiation
(λ=0.71073 Å). Starting models for structure refinement were
found using direct methods (SHELXS-97[47]) and refined against F2
by the full-matrix least-squares technique, using the SHELXL-2014/
7,[48] incorporated in WINGX-v2014.1 crystallographic collective
package.[49] Non-hydrogen atoms were found from the different
Fourier maps and refined with anisotropic displacement parame-
ters. Hydrogen atoms were placed in calculated positions with
isotropic displacement parameters. Experimental details for X-ray
data collection and the refinements are summarized in Table 3.
Synthesis of 3-(Salicylideneimino)benzonitrile (Hsal-3-PhCN). The
synthetic process for Hsal-3-PhCN was based on a previous report[29]
but under a modified condition. A methanol solution (10 mL) of 3-
aminobenzonitrile (0.59 g, 5.0 mmol) was added into a methanol
solution (5 mL) of salicylaldehyde (0.52 mL, 5.0 mmol) under nitro-
gen atmosphere. The mixture was allowed to stir for 4 h at room
temperature, and then the solvent was removed under reduced
pressure. The resultant crush products were washed with methanol
to give pure Hsal-3-PhCN as pale-yellow powders. Yield 48%
(0.53 g, 2.4 mmol). 1H NMR (300 MHz, DMSO-d6, ppm): δ 12.52 (br, s,
1H), 8.99 (s, 1H), 7.93 (s, 1H), 7.92–7.72 (m, 2H), 7.69–7.61 (m, 2H),
7.44 (td, J=8.1, 1.8 Hz, 1H), 7.00 (d, J=7.5 Hz, 1H), 6.98 (d, J=
8.4 Hz, 1H). MS (MALDI-TOF+): m/z 223.046 [M+H]+. IR (KBr pellet,
cmÀ 1): 2226 (νC�N), 1614 (νC=N). Anal. calcd for C14H10N2O: C, 75.66; H,
4.54; N, 12.60%. Found: C, 75.64; H, 4.50; N, 12.65%. Melting point:
Deposition Numbers 2080342 (1) and 2080343 (2) contain the
supplementary crystallographic data for this paper. These data are
provided free of charge by the joint Cambridge Crystallographic
Data Centre and Fachinformationszentrum Karlsruhe Access Struc-
tures service www.ccdc.cam.ac.uk/structures.
Acknowledgements
We gratefully acknowledge the National Chi Nan University and
the Ministry of Science and Technology of Taiwan (NSC 98-2113-
M-260-004-MY2 and MOST 108-2113-M-260-002-) for the financial
°
114–115 C.
Synthesis of [Zn(sal-3-PhCN)2] (1). A methanol solution (12 mL) of
Zn(BF4)2 ·xH2O (239.0 mg, 1.0 mmol) was added into a THF solution
(10 mL) of Hsal-3-PhCN (444.0 mg, 2.0 mmol) under nitrogen
atmosphere. The mixture was allowed to stir for 10 min, and then
NEt3 (99%, 18 drops, pH=8–9) was added. The resultant solution
was allowed to stir at room temperature overnight. The solvent was
removed under reduced pressure and then washed with methanol.
The resulting bright yellow precipitates were filtered. Yield 67%
Table 3. Crystallographic data for zinc-salicyaldimine compounds 1 and 2.
1
2
Empirical formula
Mw
Crystal system
Space group
C28H18N4O2Zn
507.83
Triclinic
C20H25Cl2N3OZn
459.70
Monoclinic
P21/c
1
�
P1
(340.0 mg, 0.67 mmol). H NMR (300 MHz, DMSO-d6, δ): 8.55 (s, 2H),
a [Å]
b [Å]
c [Å]
8.5050(3)
11.0636(4)
12.5338(5)
74.1250(10)
78.2890(10)
88.0510(10)
1110.50(7)
2
13.3207(7)
24.6763(13)
14.2982(9)
90
113.289(2)
90
4317.0(4)
8
150(2)
0.71073
1.415
7.86 (s, 2H), 7.68 (d, J=6.9 Hz, 4H), 7.54 (t, J=7.8 Hz, 2H), 7.39 (dd,
J=7.8, 1.5 Hz, 2H), 7.30 (t, J=7.5 Hz, 2H), 6.65 (d, J=8.4 Hz, 2H),
6.57 (t, J=7.2 H, 2H). MS (MALDI-TOF+): m/z 507.150 [M]+. IR (KBr
pellet, cmÀ 1): 2230 (νC�N), 1608 (νC=N). Anal. Calcd for C28H18N4O2Zn:
C, 66.22; H, 3.57; N, 11.03%. Found: C, 65.27; H, 3.54; N, 10.81%.
°
α [ ]
°
β [ ]
°
γ [ ]
V [Å3]
Z
°
Melting point: 224–226 C. Yellow plate-shaped single crystals
suitable for X-ray diffraction were obtained by quietly staying the
dichloromethane (CH2Cl2) solution of [Zn(sal-3-PhCN)2] (1) at room
temperature for one week.
T [K]
296(2)
0.71073
1.519
λ [Å]
Dcalc [g cmÀ 3
]
F000
520
1.141
1.725, 25.042
14135
3850 (0.0316)
3365
1904
1.400
2.421, 27.894
71401
10273 (0.0521)
9072
Synthesis of [HNEt3][Zn(sal-3-PhCN)Cl2] (2). A methanol solution
(7 mL) of ZnCl2 (136.3 mg, 1.0 mmol) was added into a THF solution
(7 mL) of Hsal-3-PhCN (222.0 mg, 1.0 mmol) under nitrogen atmos-
phere. The mixture was allowed to stir for 10 min, and then NEt3
(99%, 16 drops, pH=8–9) was added. The resultant solution was
allowed to stir at room temperature overnight. The solvent was
removed under reduced pressure and then ethyl ether was added.
The resulting bright yellow precipitates were filtered. Yield 46%
(210.0 mg, 0.46 mmol). 1H NMR (300 MHz, DMSO-d6, ppm): δ 8.60 (s,
1H), 8.07 (s, 1H), 7.97 (d, J=7.8 Hz, 1H), 7.76 (d, J=7.5 Hz, 1H), 7.67
(d, J=8.1 Hz, 1H), 7.37 (dd, J=7.8, 1.2 Hz, 1H), 7.29 (td, J=7.8,
μ [mmÀ 1
]
°
θmin, θmax [ ]
Refl. collected
Unique refl. (Rint
Obs. refl. [I>2σ (I)]
)
Parameters
316
493
R1,[a] wR2[b] [I>2σ (I)]
R1,[a] wR2[b] [all data]
GOF on F2
0.0275, 0.0578
0.0348, 0.0603
1.048
0.319, À 0.266
0.0292, 0.0873
0.0376, 0.1028
1.161
Max., min. Δ1 [e ÅÀ 3
P
]
1.474, À 0.952
�
P
P
P
[a]R1 = jjFoj À jFcjj= jFoj.[b]wR2 =f ½wðFo2 À Fc2Þ �
½wðFo2Þ �g
.
2
2
1=2
Eur. J. Inorg. Chem. 2021, 1–10
www.eurjic.org
8
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100377
[22] L. Chen, J. Qiao, J. Xie, L. Duan, D. Zhang, L. Wang, Y. Qiu, Inorg. Chim.
support. The authors thank the Instrument Center at National
Chung Hsing University for providing valuable assistance on
Elemental Analysis and Single Crystal X-Ray Diffractometer. The
authors also acknowledge MOST for research support (MOST110-
2731-M-005-001, XRD001300, EA000100).
Acta 2009, 362, 2327–2333.
[23] H.-W. Chiang, Y.-T. Su, J.-Y. Wu, Dalton Trans. 2013, 42, 15169–15182.
[24] K.-L. Kuo, C.-C. Huang, Y.-C. Lin, Dalton Trans. 2008, 3889–3898.
[25] S. Di Bella, I. Fragalà, I. Ledoux, M. A. Diaz-Garcia, T. J. Marks, J. Am.
Chem. Soc. 1997, 119, 9550–9557.
[26] Y. Hamada, T. Sano, M. Fujita, T. Fujii, Y. Nishio, K. Shibata, Jpn. J. Appl.
Phys. 1993, 32, L511–L513.
[27] J. Xie, J. Qiao, L. Wang, J. Xie, Y. Qiu, Inorg. Chim. Acta 2005, 358, 4451–
4458.
Conflict of Interest
[28] L. De La Durantaye, T. McCormick, X. Y. Liu, S. Wang, Dalton Trans. 2006,
48, 5675–5682.
[29] M. Maiti, S. Thakurta, D. Sadhukhan, G. Pilet, G. M. Rosair, A. Nonat, L. J.
Charbonnière, S. Mitra, Polyhedron 2013, 65, 6–15.
[30] H.-J. Xu, X.-X. Gong, H. Wang, Acta Crystallogr. Sect. E 2008, 64, o638.
[31] L. Ma, L. Lu, M. Zhu, Q. Wang, Y. Li, S. Xing, X. Fu, Z. Gao, Y. Dong,
Dalton Trans. 2011, 40, 6532–6540.
The authors declare no conflict of interest.
Keywords: Anion effect · Fluorescence · Salicyaldimine · Zinc
[32] M. D. Jones, M. G. Davidson, C. G. Keir, L. M. Hughes, M. F. Nahon, D. C.
Apperley, Eur. J. Inorg. Chem. 2009, 635–642.
[33] L. R. Snyder, J. Chromatogr. 1974, 92, 223–230.
[34] L. Gao, Y. Wang, J. Wang, L. Huang, L. Shi, X. Fan, Z. Zou, T. Yu, M. Zhu,
Z. Li, Inorg. Chem. 2006, 45, 6844–6850.
[35] S.-N. Li, Q.-G. Zhai, M.-C. Hu, Y.-C. Jiang, Inorg. Chim. Acta 2009, 362,
2217–2221.
[36] D. Das, B. G. Chand, K. K. Sarker, J. Dinda, C. Sinha, Polyhedron 2006, 25,
[1] X.-X. Zhou, Y.-P. Cai, S.-Z. Zhu, Q.-G. Zhan, M.-S. Liu, Z.-Y. Zhou, L. Chen,
Cryst. Growth Des. 2008, 8, 2076–2079.
[2] T. Yu, W. Su, W. Li, Z. Hong, R. Hua, M. Li, B. Chu, B. Li, Z. Zhang, Z. Z. Hu,
Inorg. Chim. Acta 2006, 359, 2246–2251.
[3] Y. Z. Shen, H. W. Gu, Y. Pan, G. Dong, T. Wu, X. P. Jin, X. Y. Huang, H. W.
Hu, J. Organomet. Chem. 2000, 605, 234–238.
[4] G. A. Morris, H. Zhou, C. L. Stern, S. B. T. Nguyen, Inorg. Chem. 2001, 40,
3222–3227.
[5] S. Bhunora, J. Mugo, A. Bhaw-Luximon, S. Mapolie, J. Van Wyk, J.
Darkwa, E. Nordlander, Appl. Organomet. Chem. 2011, 25, 133–145.
[6] S. Naiya, H. S. Wang, M. G. Drew, Y. Song, A. Ghosh, Dalton Trans. 2011,
40, 2744–2756.
[7] P. Mukherjee, M. G. Drew, C. J. Gomez-Garcia, A. Ghosh, Inorg. Chem.
2009, 48, 5848–5860.
[8] M. Shellaiah, Y.-H. Wu, A. Singh, M. V. R. Raju, H.-C. Lin, J. Mater. Chem. A
2013, 1, 1310–1318.
[9] K. B. Kim, H. Kim, E. J. Song, S. Kim, I. Noh, C. Kim, Dalton Trans. 2013,
42, 16569–16577.
[10] R. Pandey, P. Kumar, A. K. Singh, M. Shahid, P.-z. Li, S. K. Singh, Q. Xu, A.
Misra, D. S. Pandey, Inorg. Chem. 2011, 50, 3189–3197.
[11] W. A. Zoubi, S. G. Mohamed, A. A. S. Al-Hamdani, A. P. Mahendradhany,
Y. G. Ko, RSC Adv. 2018, 8, 23294–23318.
[12] C. P. Matos, Y. Addis, P. Nunes, S. Barroso, I. Alho, M. Martins, A. P. A.
Matos, F. Marques, I. Cavaco, J. C. Pessoa, I. Correia, J. Inorg. Biochem.
2019, 198, 110727.
[13] C. J. Whiteoak, G. Salassa, A. W. Kleij, Chem. Soc. Rev. 2012, 41, 622–631.
[14] J.-Y. Wu, C.-Y. Chang, C.-J. Tsai, J.-J. Lee, Inorg. Chem. 2015, 54, 10918–
10924.
[15] Y.-J. Tseng, J.-Y. Wu, Inorg. Chim. Acta 2017, 455, 241–246.
[16] C. J. Frederickson, J.-Y. Koh, A. I. Bush, Nat. Rev. Neurosci. 2005, 6, 449–
462.
2333–2340.
[37] S. Basak, S. Sen, C. Marschner, J. Baumgartner, S. R. Batten, D. R. Turner,
S. Mitra, Polyhedron 2008, 27, 1193–1200.
[38] N. J. Williams, W. Gan, J. H. Reibenspies, R. D. Hancock, Inorg. Chem.
2009, 48, 1407–1415.
[39] S. Shit, M. Nandy, D. Saha, L. Zhang, W. Schmitt, C. Rizzoli, T. N. G. Row,
J. Coord. Chem. 2016, 69, 2403–2414.
[40] M. Jayendran, P. M. S. Begum, M. R. P. Kurup, J. Mol. Struct. 2020, 1206,
127682.
[41] T.-H. Ma, M. Dong, Y.-M. Dong, Y.-W. Wang, Y. Peng, Chem. Eur. J. 2010,
16, 10313–10318.
[42] L. Xue, Q. Liu, H. Jiang, Org. Lett. 2009, 11, 3454–3457.
[43] D. Ray, P. K. Bharadwaj, Inorg. Chem. 2008, 47, 2252–2254.
[44] J.-R. Sheng, F. Feng, Y. Qiang, F.-G. Liang, L. Sen, F.-H. Wei, Anal. Lett.
2008, 41, 2203–2213.
[45] J.-S. Wu, W.-M. Liu, X.-Q. Zhuang, F. Wang, P.-F. Wang, S.-L. Tao, X.-H.
Zhang, S.-K. Wu, S.-T. Lee, Org. Lett. 2007, 9, 33–36.
[46] Y. W. Choi, G. J. Park, Y. J. Na, H. Y. Jo, S. A. Lee, G. R. You, C. Kim, Sens.
Actuators B 2014, 194, 343–352.
[47] G. M. Sheldrick, Acta Crystallogr. Sect. A 2008, 64, 112–122.
[48] G. M. Sheldrick, Acta Crystallogr. Sect. C 2015, 71, 3–8.
[49] L. J. Farrugia, J. Appl. Crystallogr. 2012, 45, 849–854.
[17] P. J. Jiang, Z. J. Guo, Coord. Chem. Rev. 2004, 248, 205–229.
[18] N. C. Lim, H. C. Freake, C. Bruckner, Chem. Eur. J. 2004, 11, 38–49.
[19] A. Barbieri, G. Accorsi, N. Armaroli, Chem. Commun. 2008, 2185–2193.
[20] R. Diana, B. Panunzi, Molecules 2020, 25, 4984.
[21] M. Prabhakar, P. S. Zacharias, S. K. Das, Inorg. Chem. 2005, 44, 2585–
2587.
Manuscript received: May 4, 2021
Revised manuscript received: July 9, 2021
Accepted manuscript online: July 13, 2021
Eur. J. Inorg. Chem. 2021, 1–10
www.eurjic.org
9
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

FULL PAPERS
Dr. M.-J. Tsai, Y.-T. Su, Prof. Dr. J.-Y.
Wu*
1 – 10
Anion Effect on the Formation of
Zinc-Salicyaldimine Compounds
in Neutral and Anionic Complex
Forms: Synthesis, Characteriza-
tion, 1H NMR Studies, and Photo-
physical Properties
Anion Effect: Anion shows remarkable
domination on the formation of
neutral and ionic zinc-salicyaldimine
compounds, of which the ionic one
exhibits solvent-dependent equilibria
of decomplxation and recomplexa-
tion.